Advertisement

Neil2-null Mice Accumulate Oxidized DNA Bases in the Transcriptionally Active Sequences of the Genome and Are Susceptible to Innate Inflammation*

Open AccessPublished:August 05, 2015DOI:https://doi.org/10.1074/jbc.M115.658146
      Why mammalian cells possess multiple DNA glycosylases (DGs) with overlapping substrate ranges for repairing oxidatively damaged bases via the base excision repair (BER) pathway is a long-standing question. To determine the biological role of these DGs, null animal models have been generated. Here, we report the generation and characterization of mice lacking Neil2 (Nei-like 2). As in mice deficient in each of the other four oxidized base-specific DGs (OGG1, NTH1, NEIL1, and NEIL3), Neil2-null mice show no overt phenotype. However, middle-aged to old Neil2-null mice show the accumulation of oxidative genomic damage, mostly in the transcribed regions. Immuno-pulldown analysis from wild-type (WT) mouse tissue showed the association of NEIL2 with RNA polymerase II, along with Cockayne syndrome group B protein, TFIIH, and other BER proteins. Chromatin immunoprecipitation analysis from mouse tissue showed co-occupancy of NEIL2 and RNA polymerase II only on the transcribed genes, consistent with our earlier in vitro findings on NEIL2's role in transcription-coupled BER. This study provides the first in vivo evidence of genomic region-specific repair in mammals. Furthermore, telomere loss and genomic instability were observed at a higher frequency in embryonic fibroblasts from Neil2-null mice than from the WT. Moreover, Neil2-null mice are much more responsive to inflammatory agents than WT mice. Taken together, our results underscore the importance of NEIL2 in protecting mammals from the development of various pathologies that are linked to genomic instability and/or inflammation. NEIL2 is thus likely to play an important role in long term genomic maintenance, particularly in long-lived mammals such as humans.

      Introduction

      Endogenously generated reactive oxygen species in mammalian cells continuously target cellular macromolecules, including the genomic DNA (
      • Ames B.N.
      • Shigenaga M.K.
      • Hagen T.M.
      Oxidants, antioxidants, and the degenerative diseases of aging.
      ,
      • Kasai H.
      • Nishimura S.
      ,
      • Halliwell B.
      Free radicals, antioxidants, and human disease: curiosity, cause, or consequence?.
      ). However, all cells are equipped with an arsenal of DNA repair proteins that continuously maintain the genome's integrity for proper cellular function and viability. Reactive oxygen species-induced oxidative DNA base modifications are primarily repaired via the base excision repair (BER)
      The abbreviations used are: BER
      base excision repair
      Ab
      antibody
      co-IP
      co-immunoprecipitation
      CSB
      Cockayne syndrome group B protein
      IP
      immunoprecipitate
      MEF
      mouse embryonic fibroblast
      TC-BER
      transcription-coupled base excision repair
      TCR
      transcription-coupled repair
      BisTris
      2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol
      qPCR
      quantitative PCR
      RNAP
      RNA polymerase
      LA-qPCR
      long amplicon-quantitative PCR
      GOx
      glucose oxidase
      oligo
      oligonucleotide
      Lig
      ligase.
      pathway, which is initiated with excision of the oxidized base by a DNA glycosylase/AP lyase, generating 3′-blocked ends and 5′-phosphate. The 3′ end is then processed to generate 3′-OH, which is necessary for DNA polymerase to incorporate the appropriate base using the nondamaged template base, and finally nick-sealing by a DNA ligase (
      • Hazra T.K.
      • Das A.
      • Das S.
      • Choudhury S.
      • Kow Y.W.
      • Roy R.
      Oxidative DNA damage repair in mammalian cells: a new perspective.
      ,
      • Hegde M.L.
      • Hazra T.K.
      • Mitra S.
      Early steps in the DNA base excision/single-strand interruption repair pathway in mammalian cells.
      ). In human cells, five oxidized base-specific DNA glycosylases have been identified and characterized so far. Endonuclease III homolog 1 (NTH1) and 8-oxoguanine-DNA glycosylase (OGG1) were characterized initially by several groups; these enzymes preferentially excise oxidized pyrimidines and purines, respectively (
      • Ikeda S.
      • Biswas T.
      • Roy R.
      • Izumi T.
      • Boldogh I.
      • Kurosky A.
      • Sarker A.H.
      • Seki S.
      • Mitra S.
      Purification and characterization of human hNTH1, a homolog of Escherichia coli endonuclease III: direct identification of Lys-212 as the active nucleophilic residue.
      ,
      • Lu R.
      • Nash H.M.
      • Verdine G.L.
      A DNA repair enzyme that excises oxidatively damaged guanines from the mammalian genome is frequently lost in lung cancer.
      ). Several years later, we and others identified NEIL (Nei-like 1–3) DNA glycosylases, which are functionally similar to Escherichia coli MutM or Nei and excise both purine and pyrimidine oxidation products (
      • Hazra T.K.
      • Izumi T.
      • Boldogh I.
      • Imhoff B.
      • Kow Y.W.
      • Jaruga P.
      • Dizdaroglu M.
      • Mitra S.
      Identification and characterization of a human DNA glycosylase for repair of modified bases in oxidatively damaged DNA.
      ,
      • Bandaru V.
      • Sunkara S.
      • Wallace S.S.
      • Bond J.P.
      A novel human DNA glycosylase that removes oxidative DNA damage and is homologous to Escherichia coli endonuclease VIII.
      ,
      • Takao M.
      • Kanno S.
      • Shiromoto T.
      • Hasegawa R.
      • Ide H.
      • Ikeda S.
      • Sarker A.H.
      • Seki S.
      • Xing J.Z.
      • Le X.C.
      • Weinfeld M.
      • Kobayashi K.
      • Miyazaki J.
      • Muijtjens M.
      • Hoeijmakers J.H.
      • et al.
      Novel nuclear and mitochondrial glycosylases revealed by disruption of the mouse Nth1 gene encoding an endonuclease III homolog for repair of thymine glycols.
      ,
      • Liu M.
      • Bandaru V.
      • Bond J.P.
      • Jaruga P.
      • Zhao X.
      • Christov P.P.
      • Burrows C.J.
      • Rizzo C.J.
      • Dizdaroglu M.
      • Wallace S.S.
      The mouse ortholog of NEIL3 is a functional DNA glycosylase in vitro and in vivo.
      ,
      • Hazra T.K.
      • Kow Y.W.
      • Hatahet Z.
      • Imhoff B.
      • Boldogh I.
      • Mokkapati S.K.
      • Mitra S.
      • Izumi T.
      Identification and characterization of a novel human DNA glycosylase for repair of cytosine-derived lesions.
      ). All three NEILs excise base lesions from DNA bubble or single-stranded regions; in contrast, NTH1 and OGG1 are active only with duplex DNA (
      • Dou H.
      • Mitra S.
      • Hazra T.K.
      Repair of oxidized bases in DNA bubble structures by human DNA glycosylases NEIL1 and NEIL2.
      ,
      • Krokeide S.Z.
      • Laerdahl J.K.
      • Salah M.
      • Luna L.
      • Cederkvist F.H.
      • Fleming A.M.
      • Burrows C.J.
      • Dalhus B.
      • Bjørås M.
      Human NEIL3 is mainly a monofunctional DNA glycosylase removing spiroimindiohydantoin and guanidinohydantoin.
      ,
      • Aamann M.D.
      • Hvitby C.
      • Popuri V.
      • Muftuoglu M.
      • Lemminger L.
      • Skeby C.K.
      • Keijzers G.
      • Ahn B.
      • Bjørås M.
      • Bohr V.A.
      • Stevnsner T.
      Cockayne Syndrome group B protein stimulates NEIL2 DNA glycosylase activity.
      ). We have recently reported that NEIL1 is primarily involved in the repair of replicating genomes (
      • Dou H.
      • Theriot C.A.
      • Das A.
      • Hegde M.L.
      • Matsumoto Y.
      • Boldogh I.
      • Hazra T.K.
      • Bhakat K.K.
      • Mitra S.
      Interaction of the human DNA glycosylase NEIL1 with proliferating cell nuclear antigen. The potential for replication-associated repair of oxidized bases in mammalian genomes.
      ,
      • Hegde M.L.
      • Hegde P.M.
      • Bellot L.J.
      • Mandal S.M.
      • Hazra T.K.
      • Li G.M.
      • Boldogh I.
      • Tomkinson A.E.
      • Mitra S.
      Prereplicative repair of oxidized bases in the human genome is mediated by NEIL1 DNA glycosylase together with replication proteins.
      ), and our in vitro biochemical studies indicate that NEIL2 primarily removes the oxidized bases from transcribing genes via a transcription-coupled BER (TC-BER) pathway (
      • Banerjee D.
      • Mandal S.M.
      • Das A.
      • Hegde M.L.
      • Das S.
      • Bhakat K.K.
      • Boldogh I.
      • Sarkar P.S.
      • Mitra S.
      • Hazra T.K.
      Preferential repair of oxidized base damage in the transcribed genes of mammalian cells.
      ). We also identified a polymorphic variant of NEIL2 that occurs more frequently in human lung cancer patients than in normal individuals (
      • Dey S.
      • Maiti A.K.
      • Hegde M.L.
      • Hegde P.M.
      • Boldogh I.
      • Sarkar P.S.
      • Abdel-Rahman S.Z.
      • Sarker A.H.
      • Hang B.
      • Xie J.
      • Tomkinson A.E.
      • Zhou M.
      • Shen B.
      • Wang G.
      • Wu C.
      • Yu D.
      • et al.
      Increased risk of lung cancer associated with a functionally impaired polymorphic variant of the DNA glycosylase NEIL2.
      ). Furthermore, depletion of NEIL2 caused a significant increase in the spontaneous mutation frequency in the HPRT gene of the V79 Chinese hamster lung cell line (
      • Maiti A.K.
      • Boldogh I.
      • Spratt H.
      • Mitra S.
      • Hazra T.K.
      Mutator phenotype of mammalian cells due to deficiency of NEIL1 DNA glycosylase, an oxidized base-specific repair enzyme.
      ). All these studies collectively indicate that NEIL2 plays an important role in maintaining genomic integrity and preventing DNA mutagenesis in mammalian cells.
      To examine the biological significance of NEIL2, we generated Neil2-knock-out (KO) mice. The Neil2-KO mice were overtly normal and fertile; however, we found that they accumulated higher amounts of oxidized bases in the transcribed region of the genome as they aged. Moreover, Neil2-null MEFs showed a significantly higher frequency of telomere loss and genome instability, indicating a critical role of NEIL2 in long term genomic maintenance.

      Discussion

      Five oxidized base-specific DNA glycosylases with overlapping substrate specificities are involved in the repair of approximately 24 oxidized DNA bases via the BER pathway in mammalian cells. To examine the in vivo role of these DNA glycosylases, gene knock-out mice for four DNA glycosylases (Ogg1, Nth1, Neil1, and Neil3) have already been generated (
      • Klungland A.
      • Rosewell I.
      • Hollenbach S.
      • Larsen E.
      • Daly G.
      • Epe B.
      • Seeberg E.
      • Lindahl T.
      • Barnes D.E.
      Accumulation of premutagenic DNA lesions in mice defective in removal of oxidative base damage.
      ,
      • Ocampo M.T.
      • Chaung W.
      • Marenstein D.R.
      • Chan M.K.
      • Altamirano A.
      • Basu A.K.
      • Boorstein R.J.
      • Cunningham R.P.
      • Teebor G.W.
      Targeted deletion of mNth1 reveals a novel DNA repair enzyme activity.
      ,
      • Vartanian V.
      • Lowell B.
      • Minko I.G.
      • Wood T.G.
      • Ceci J.D.
      • George S.
      • Ballinger S.W.
      • Corless C.L.
      • McCullough A.K.
      • Lloyd R.S.
      The metabolic syndrome resulting from a knockout of the NEIL1 DNA glycosylase.
      ,
      • Torisu K.
      • Tsuchimoto D.
      • Ohnishi Y.
      • Nakabeppu Y.
      Hematopoietic tissue-specific expression of mouse Neil3 for endonuclease VIII-like protein.
      ). We report here for the first time the generation of a Neil2-null mouse strain that lacks the NEIL2 DNA glycosylase. Our strategy involved Cre-mediated targeted disruption of exon 2 of mNeil2, which is critical for its enzymatic activity. Our data showed that the transcripts and NEIL2 protein are absent in the homozygous mutant animals. Neil2-null mice, like the other four DNA glycosylase loss-of-function mouse models, did not show any obvious abnormality or spontaneous tumorigenesis. Surprisingly, knock-out animal models of the other components in the BER pathways, downstream of DNA glycosylases (such as APE1, pol β, and Lig IIIα), are embryonic lethal (
      • Gu H.
      • Marth J.D.
      • Orban P.C.
      • Mossmann H.
      • Rajewsky K.
      Deletion of a DNA polymerase β gene segment in T cells using cell type-specific gene targeting.
      ,
      • Sugo N.
      • Aratani Y.
      • Nagashima Y.
      • Kubota Y.
      • Koyama H.
      Neonatal lethality with abnormal neurogenesis in mice deficient in DNA polymerase β.
      ,
      • Izumi T.
      • Brown D.B.
      • Naidu C.V.
      • Bhakat K.K.
      • Macinnes M.A.
      • Saito H.
      • Chen D.J.
      • Mitra S.
      Two essential but distinct functions of the mammalian abasic endonuclease.
      ,
      • Puebla-Osorio N.
      • Lacey D.B.
      • Alt F.W.
      • Zhu C.
      Early embryonic lethality due to targeted inactivation of DNA ligase III.
      ). This suggests that DNA glycosylase-mediated repair intermediates (AP sites or strand breaks) are lethal to the whole organism.
      Using a cell culture model, we have reported earlier that NEIL2 initiates the repair of oxidized bases preferentially from the transcribed genes, and also characterized the NEIL2-mediated TC-BER biochemically using an in vitro reconstituted repair system (
      • Banerjee D.
      • Mandal S.M.
      • Das A.
      • Hegde M.L.
      • Das S.
      • Bhakat K.K.
      • Boldogh I.
      • Sarkar P.S.
      • Mitra S.
      • Hazra T.K.
      Preferential repair of oxidized base damage in the transcribed genes of mammalian cells.
      ). In this study, we further evaluated the age-dependent accumulation of spontaneously generated oxidative genome damage in various tissues of Neil2-null and WT mice. Gene-specific analysis of oxidative genome damage by LA-qPCR clearly demonstrated that young (2 months) Neil2-null mice do not show a significant amount of DNA damage accumulation. However, middle age (8 months) and old age (24 months) animals do accumulate significant amounts of oxidative DNA lesions, mostly in the transcribed but not in the nontranscribed genes of various tissues, further implicating NEIL2's biological role in TC-BER. Two other reports also have indicated transcription-coupled repair of oxidized bases in mammalian cells, as well as in yeast (
      • Reis A.M.
      • Mills W.K.
      • Ramachandran I.
      • Friedberg E.C.
      • Thompson D.
      • Queimado L.
      Targeted detection of in vivo endogenous DNA base damage reveals preferential base excision repair in the transcribed strand.
      ,
      • Guo J.
      • Hanawalt P.C.
      • Spivak G.
      Comet-FISH with strand-specific probes reveals transcription coupled repair of 8-oxoguanine in human cells.
      ). To our knowledge, ours is the first in vivo evidence for such repair of oxidized bases in mammals.
      Given the role of NEIL2 in TC-BER, we have analyzed physiologically relevant protein-protein interactions/associations using mouse tissue extracts, and we have shown NEIL2's preferential association with the transcribed genes and the co-association of RNAP II and several critical TCR-related proteins in a complex with NEIL2 and Lig IIIα. Our partial characterization of NEIL2 and Lig IIIα immunocomplexes demonstrates that NEIL2 and Lig IIIα co-opt CSB and TFIIH, two critical TC-nucleotide excision repair proteins. A recent study by Aamann et al. (
      • Aamann M.D.
      • Hvitby C.
      • Popuri V.
      • Muftuoglu M.
      • Lemminger L.
      • Skeby C.K.
      • Keijzers G.
      • Ahn B.
      • Bjørås M.
      • Bohr V.A.
      • Stevnsner T.
      Cockayne Syndrome group B protein stimulates NEIL2 DNA glycosylase activity.
      ) reported that CSB physically interacts with and stimulates NEIL2's activity in transcription bubble-mimic DNA. Several studies have also shown that CSB cooperates in enhancing RNAP II-mediated transcription, and TFIIH helps remodel stalled RNAP II for allowing repair proteins to access the DNA lesion during TCR (
      • Sarker A.H.
      • Tsutakawa S.E.
      • Kostek S.
      • Ng C.
      • Shin D.S.
      • Peris M.
      • Campeau E.
      • Tainer J.A.
      • Nogales E.
      • Cooper P.K.
      Recognition of RNA polymerase II and transcription bubbles by XPG, CSB, and TFIIH: insights for transcription-coupled repair and Cockayne syndrome.
      ,
      • Selby C.P.
      • Sancar A.
      Cockayne syndrome group B protein enhances elongation by RNA polymerase II.
      ,
      • Tantin D.
      • Kansal A.
      • Carey M.
      Recruitment of the putative transcription-repair coupling factor CSB/ERCC6 to RNA polymerase II elongation complexes.
      ). Hence, the association of TCR-related proteins with both NEIL2 and Lig IIIα, respectively, the first and last enzyme in the BER pathway, is consistent with NEIL2's role in TC-BER. TC-BER is obviously a complex process, and many more proteins are likely to be involved with NEIL2 forming a multiprotein complex. Identification of additional proteins and their role in TC-BER thus warrants further investigation.
      Several studies have indicated that BER deficiency and/or persistent oxidative DNA base accumulation interfere with telomere length homoeostasis and overall genomic integrity (
      • Vallabhaneni H.
      • O'Callaghan N.
      • Sidorova J.
      • Liu Y.
      Defective repair of oxidative base lesions by the DNA glycosylase Nth1 associates with multiple telomere defects.
      ,
      • Wang Z.
      • Rhee D.B.
      • Lu J.
      • Bohr C.T.
      • Zhou F.
      • Vallabhaneni H.
      • de Souza-Pinto N.C.
      • Liu Y.
      Characterization of oxidative guanine damage and repair in mammalian telomeres.
      ). We have shown here that primary Neil2-null MEFs undergo severe telomere loss at chromosome ends, indicating NEIL2's important role in telomere maintenance. Notably, several recent studies have demonstrated that RNAP II transcribes the chromosomal ends into a variety of noncoding RNA species, including telomeric repeat-containing RNA constituting a “telomeric transcriptome” (
      • Bah A.
      • Azzalin C.M.
      The telomeric transcriptome: from fission yeast to mammals.
      ,
      • Porro A.
      • Feuerhahn S.
      • Delafontaine J.
      • Riethman H.
      • Rougemont J.
      • Lingner J.
      Functional characterization of the TERRA transcriptome at damaged telomeres.
      ). Therefore, it is likely that NEIL2-mediated TC-BER plays a critical role therein as well. Importantly, the majority of somatic human cells express a low level of telomerase; hence, inactive or low levels of NEIL2 could have a significant impact on telomere maintenance and genome stability in human tissues.
      Despite NEIL2's role in the repair of the transcribing genome, why the KO animals do not show any apparent phenotype is not clear to us at present. Although the mouse has been extensively used as a model organism in the study of human biology and diseases, it has been found that >20% of essential human genes have nonessential mouse orthologs (
      • Liao B.Y.
      • Zhang J.
      Null mutations in human and mouse orthologs frequently result in different phenotypes.
      ). These discrepancies may be caused by adaptive evolution for the prolonged life span in humans. The age-dependent increase in the accumulation of oxidatively damaged bases in the transcribed genes of Neil2-null mice indicates NEIL2's critical role in long term genomic maintenance. Hence, caution should be used in extrapolating the animal data while addressing the physiological importance of the human gene based on the animal data.
      Oxidative DNA damage levels are elevated in many pathological conditions; however, no incidence of carcinogenesis has been reported in many cases (
      • Cooke M.S.
      • Evans M.D.
      • Dizdaroglu M.
      • Lunec J.
      Oxidative DNA damage: mechanisms, mutation, and disease.
      ). It is important to mention here that Ogg1−/− mice, despite the accumulation of ∼250-fold higher amounts of mutagenic 8-oxoG compared with WT mice in their genomes due to KBrO3 (an oxygen radical-forming agent) exposure, did not show any tumor formation (
      • Arai T.
      • Kelly V.P.
      • Minowa O.
      • Noda T.
      • Nishimura S.
      The study using wild-type and Ogg1 knockout mice exposed to potassium bromate shows no tumor induction despite an extensive accumulation of 8-hydroxyguanine in kidney DNA.
      ). This suggests that DNA damage in the genome alone is not sufficient for tumor formation, a promoting process or impairment of another parallel/back-up pathway is necessary. Recently, an international consortium comprehensively analyzed germ line mutation carriers (∼24,000) in the BRCA1 and BRCA2 genes and their correlation to a lifetime risk of developing breast and ovarian cancer. They found that the age of disease onset is highly variable, and not all BRCA carriers develop cancer, indicating the involvement of other genetic factors or modifier genes. Surprisingly, one minor allele of NEIL2 was found to be associated with breast cancer risk in BRCA2 mutation carriers and an OGG1 SNP with the risk of ovarian cancer in BRCA1 carriers (
      • Osorio A.
      • Milne R.L.
      • Kuchenbaecker K.
      • Vaclová T.
      • Pita G.
      • Alonso R.
      • Peterlongo P.
      • Blanco I.
      • de la Hoya M.
      • Duran M.
      • Díez O.
      • Ramon Y.C.
      • Konstantopoulou I.
      • Martínez-Bouzas C.
      • Andrés Conejero R.
      • et al.
      DNA glycosylases involved in base excision repair may be associated with cancer risk in BRCA1 and BRCA2 mutation carriers.
      ). Because the Neil2-null mice are living in a stress-free environment, the other genetic or environmental factors may modify the risk of pathogenic development. We thus postulate that double-mutant (Neil2 and Brca2) animals will develop aggressive breast cancer at a very early stage.
      Several recent studies have indicated that in addition to its primary function in BER, OGG1 plays a role in cell signaling, gene expression, and modulating allergic inflammatory responses. Specifically, we have shown that OGG1 in complex with 8-oxoG base (repair product) induces an inflammatory response in the lungs via K-RAS-MAPK, PI3K, and MS kinase and the NF-κB pathway (
      • Aguilera-Aguirre L.
      • Bacsi A.
      • Radak Z.
      • Hazra T.K.
      • Mitra S.
      • Sur S.
      • Brasier A.R.
      • Ba X.
      • Boldogh I.
      Innate inflammation induced by the 8-oxoguanine DNA glycosylase-1-KRAS-NF-κB pathway.
      ,
      • Ba X.
      • Bacsi A.
      • Luo J.
      • Aguilera-Aguirre L.
      • Zeng X.
      • Radak Z.
      • Brasier A.R.
      • Boldogh I.
      8-Oxoguanine DNA glycosylase-1 augments proinflammatory gene expression by facilitating the recruitment of site-specific transcription factors.
      ). These observations are consistent with the earlier observation that Ogg1-null mice are resistant to innate and allergic airway inflammation (
      • Bacsi A.
      • Aguilera-Aguirre L.
      • Szczesny B.
      • Radak Z.
      • Hazra T.K.
      • Sur S.
      • Ba X.
      • Boldogh I.
      Down-regulation of 8-oxoguanine DNA glycosylase 1 expression in the airway epithelium ameliorates allergic lung inflammation.
      ) and LPS-induced organ dysfunction and inflammatory cell infiltration (
      • Mabley J.G.
      • Pacher P.
      • Deb A.
      • Wallace R.
      • Elder R.H.
      • Szabó C.
      Potential role for 8-oxoguanine DNA glycosylase in regulating inflammation.
      ). By contrast, this study demonstrates that Neil2-null mice are extremely susceptible to inflammation induced by pro-inflammatory agents such as LPS, TNFα, and oxidative stress that utilize distinct signaling pathways. LPS activates inflammatory signaling via a TLR4-MD2 complex (
      • Nijland R.
      • Hofland T.
      • van Strijp J.A.
      Recognition of LPS by TLR4: potential for antiinflammatory therapies.
      ,
      • da Silva Correia J.
      • Soldau K.
      • Christen U.
      • Tobias P.S.
      • Ulevitch R.J.
      Lipopolysaccharide is in close proximity to each of the proteins in its membrane receptor complex. Transfer from CD14 to TLR4 and MD-2.
      ), whereas TNF-α has been shown to signal via distinct cell surface receptors TNFR-1 and TNFR-2 (
      • Jamaluddin M.
      • Wang S.
      • Boldogh I.
      • Tian B.
      • Brasier A.R.
      TNF-α-induced NF-κB/RelA Ser (276) phosphorylation and enhanceosome formation is mediated by an ROS-dependent PKAc pathway.
      ,
      • Choudhary S.
      • Kalita M.
      • Fang L.
      • Patel K.V.
      • Tian B.
      • Zhao Y.
      • Edeh C.B.
      • Brasier A.R.
      Inducible tumor necrosis factor (TNF) receptor-associated factor-1 expression couples the canonical to the non-canonical NFκB pathway in TNF stimulation.
      ). In contrast, GOx primarily generates superoxide anions to activate inflammatory signaling via redox-reactive kinases (
      • Aguilera-Aguirre L.
      • Bacsi A.
      • Radak Z.
      • Hazra T.K.
      • Mitra S.
      • Sur S.
      • Brasier A.R.
      • Ba X.
      • Boldogh I.
      Innate inflammation induced by the 8-oxoguanine DNA glycosylase-1-KRAS-NF-κB pathway.
      ,
      • Das A.
      • Hazra T.K.
      • Boldogh I.
      • Mitra S.
      • Bhakat K.K.
      Induction of the human oxidized base-specific DNA glycosylase NEIL1 by reactive oxygen species.
      ). To our surprise, Neil2 KO mice were highly susceptible to LPS- and GOx-induced inflammation, although their sensitivity to TNF-α (one of the most potent inflammatory cytokines) was modest (
      • Tian B.
      • Nowak D.E.
      • Brasier A.R.
      A TNF-induced gene expression program under oscillatory NF-κB control.
      ). The mechanism of differential susceptibility of Neil2-null mice to innate inflammation requires extensive study. Nonetheless, taken together, all these data imply that OGG1 is involved in a pro-inflammatory but NEIL2 in an anti-inflammatory response. How these two DNA glycosylases maintain and balance the cellular inflammatory response will be an exciting area of research in the future.
      A linkage of inflammation and cancer is well established (
      • Balkwill F.
      • Mantovani A.
      Inflammation and cancer: back to Virchow?.
      ,
      • Hanahan D.
      • Weinberg R.A.
      Hallmarks of cancer: the next generation.
      ). Samson and co-workers (
      • Calvo J.A.
      • Meira L.B.
      • Lee C.Y.
      • Moroski-Erkul C.A.
      • Abolhassani N.
      • Taghizadeh K.
      • Eichinger L.W.
      • Muthupalani S.
      • Nordstrand L.M.
      • Klungland A.
      • Samson L.D.
      DNA repair is indispensable for survival after acute inflammation.
      ) recently demonstrated how chronic inflammation could contribute to carcinogenesis and the protective role of several DNA repair proteins, such as methyl purine DNA glycosylase, ALKBH2 and ALKBH3. Consistent with these findings, this study indicates that depletion of NEIL2 causes genomic instability, and it simultaneously induces innate inflammation. These combinatorial effects of genomic damage and innate inflammation due to NEIL2 deficiency could play a critical role in the development of breast cancer in BRCA2 carriers but also in other diseases as well. Notably, we and others have reported the association of some NEIL2 SNPs with lung and oropharyngeal cancer risk (
      • Dey S.
      • Maiti A.K.
      • Hegde M.L.
      • Hegde P.M.
      • Boldogh I.
      • Sarkar P.S.
      • Abdel-Rahman S.Z.
      • Sarker A.H.
      • Hang B.
      • Xie J.
      • Tomkinson A.E.
      • Zhou M.
      • Shen B.
      • Wang G.
      • Wu C.
      • Yu D.
      • et al.
      Increased risk of lung cancer associated with a functionally impaired polymorphic variant of the DNA glycosylase NEIL2.
      ,
      • Zhai X.
      • Zhao H.
      • Liu Z.
      • Wang L.E.
      • El-Naggar A.K.
      • Sturgis E.M.
      • Wei Q.
      Functional variants of the NEIL1 and NEIL2 genes and risk and progression of squamous cell carcinoma of the oral cavity and oropharynx.
      ). Therefore, understanding the molecular mechanisms of such combinatorial responses using Neil2-null mice as an experimental tool may help to explain the previously proposed link of oxidative stress and inflammation to various pathologies, and the knowledge gained from such studies should ultimately benefit human health.

      Author Contributions

      T. K. H. conceived, designed, and coordinated the research. A. C. performed experiments in Figs. 1, C and D, and FIGURE 2, FIGURE 3, FIGURE 4, FIGURE 5. M. W. generated Neil2-null mice, performed all mouse surgeries related to FIGURE 1, FIGURE 2, FIGURE 3, FIGURE 4, FIGURE 5, and performed experiments in Fig. 1B. T. V. C. had a major contribution in designing and standardizing PCR conditions in Fig. 3 and contributed to the preparation of the final figures. R. K. P. and D. K. S. performed experiments in Fig. 6. L. A. A. and K. H. performed experiments in Fig. 7. A. H. S. and I. B. derived and characterized MEFs from WT and Neil2-KO mice. T. G. W. generated constructs shown in Fig. 1A. G. S., V. C., and P. S. S. provided valuable scientific inputs and technical support. T. K. H., S. S., T. K. P., and I. B. analyzed the data. T. K. H. wrote the paper with contributions from I. B., S. S., and T. K. P. All the authors read, reviewed and approved the final version of the manuscript.

      Acknowledgments

      We thank Dr. David Konkel for critically editing this manuscript and Justin Barr of IDT for designing long amplicon quantitative PCR primers for mouse NanoG.

      References

        • Ames B.N.
        • Shigenaga M.K.
        • Hagen T.M.
        Oxidants, antioxidants, and the degenerative diseases of aging.
        Proc. Natl. Acad. Sci. U.S.A. 1993; 90: 7915-7922
        • Kasai H.
        • Nishimura S.
        Sies H. Oxidative Stress: Oxidants and Antioxidants. Academic Press, London1991: 99-116
        • Halliwell B.
        Free radicals, antioxidants, and human disease: curiosity, cause, or consequence?.
        Lancet. 1994; 344: 721-724
        • Hazra T.K.
        • Das A.
        • Das S.
        • Choudhury S.
        • Kow Y.W.
        • Roy R.
        Oxidative DNA damage repair in mammalian cells: a new perspective.
        DNA Repair. 2007; 6: 470-480
        • Hegde M.L.
        • Hazra T.K.
        • Mitra S.
        Early steps in the DNA base excision/single-strand interruption repair pathway in mammalian cells.
        Cell Res. 2008; 18: 27-47
        • Ikeda S.
        • Biswas T.
        • Roy R.
        • Izumi T.
        • Boldogh I.
        • Kurosky A.
        • Sarker A.H.
        • Seki S.
        • Mitra S.
        Purification and characterization of human hNTH1, a homolog of Escherichia coli endonuclease III: direct identification of Lys-212 as the active nucleophilic residue.
        J. Biol. Chem. 1998; 273: 21585-21593
        • Lu R.
        • Nash H.M.
        • Verdine G.L.
        A DNA repair enzyme that excises oxidatively damaged guanines from the mammalian genome is frequently lost in lung cancer.
        Curr. Biol. 1997; 7: 397-407
        • Hazra T.K.
        • Izumi T.
        • Boldogh I.
        • Imhoff B.
        • Kow Y.W.
        • Jaruga P.
        • Dizdaroglu M.
        • Mitra S.
        Identification and characterization of a human DNA glycosylase for repair of modified bases in oxidatively damaged DNA.
        Proc. Natl. Acad. Sci. U.S.A. 2002; 99: 3523-3528
        • Bandaru V.
        • Sunkara S.
        • Wallace S.S.
        • Bond J.P.
        A novel human DNA glycosylase that removes oxidative DNA damage and is homologous to Escherichia coli endonuclease VIII.
        DNA Repair. 2002; 1: 517-529
        • Takao M.
        • Kanno S.
        • Shiromoto T.
        • Hasegawa R.
        • Ide H.
        • Ikeda S.
        • Sarker A.H.
        • Seki S.
        • Xing J.Z.
        • Le X.C.
        • Weinfeld M.
        • Kobayashi K.
        • Miyazaki J.
        • Muijtjens M.
        • Hoeijmakers J.H.
        • et al.
        Novel nuclear and mitochondrial glycosylases revealed by disruption of the mouse Nth1 gene encoding an endonuclease III homolog for repair of thymine glycols.
        EMBO J. 2002; 21: 3486-3493
        • Liu M.
        • Bandaru V.
        • Bond J.P.
        • Jaruga P.
        • Zhao X.
        • Christov P.P.
        • Burrows C.J.
        • Rizzo C.J.
        • Dizdaroglu M.
        • Wallace S.S.
        The mouse ortholog of NEIL3 is a functional DNA glycosylase in vitro and in vivo.
        Proc. Natl. Acad. Sci. U.S.A. 2010; 107: 4925-4930
        • Hazra T.K.
        • Kow Y.W.
        • Hatahet Z.
        • Imhoff B.
        • Boldogh I.
        • Mokkapati S.K.
        • Mitra S.
        • Izumi T.
        Identification and characterization of a novel human DNA glycosylase for repair of cytosine-derived lesions.
        J. Biol. Chem. 2002; 277: 30417-30420
        • Dou H.
        • Mitra S.
        • Hazra T.K.
        Repair of oxidized bases in DNA bubble structures by human DNA glycosylases NEIL1 and NEIL2.
        J. Biol. Chem. 2003; 278: 49679-49684
        • Krokeide S.Z.
        • Laerdahl J.K.
        • Salah M.
        • Luna L.
        • Cederkvist F.H.
        • Fleming A.M.
        • Burrows C.J.
        • Dalhus B.
        • Bjørås M.
        Human NEIL3 is mainly a monofunctional DNA glycosylase removing spiroimindiohydantoin and guanidinohydantoin.
        DNA Repair. 2013; 12: 1159-1164
        • Aamann M.D.
        • Hvitby C.
        • Popuri V.
        • Muftuoglu M.
        • Lemminger L.
        • Skeby C.K.
        • Keijzers G.
        • Ahn B.
        • Bjørås M.
        • Bohr V.A.
        • Stevnsner T.
        Cockayne Syndrome group B protein stimulates NEIL2 DNA glycosylase activity.
        Mech. Ageing Dev. 2014; 135: 1-14
        • Dou H.
        • Theriot C.A.
        • Das A.
        • Hegde M.L.
        • Matsumoto Y.
        • Boldogh I.
        • Hazra T.K.
        • Bhakat K.K.
        • Mitra S.
        Interaction of the human DNA glycosylase NEIL1 with proliferating cell nuclear antigen. The potential for replication-associated repair of oxidized bases in mammalian genomes.
        J. Biol. Chem. 2008; 283: 3130-3140
        • Hegde M.L.
        • Hegde P.M.
        • Bellot L.J.
        • Mandal S.M.
        • Hazra T.K.
        • Li G.M.
        • Boldogh I.
        • Tomkinson A.E.
        • Mitra S.
        Prereplicative repair of oxidized bases in the human genome is mediated by NEIL1 DNA glycosylase together with replication proteins.
        Proc. Natl. Acad. Sci. U.S.A. 2013; 110: E3090-E3099
        • Banerjee D.
        • Mandal S.M.
        • Das A.
        • Hegde M.L.
        • Das S.
        • Bhakat K.K.
        • Boldogh I.
        • Sarkar P.S.
        • Mitra S.
        • Hazra T.K.
        Preferential repair of oxidized base damage in the transcribed genes of mammalian cells.
        J. Biol. Chem. 2011; 286: 6006-6016
        • Dey S.
        • Maiti A.K.
        • Hegde M.L.
        • Hegde P.M.
        • Boldogh I.
        • Sarkar P.S.
        • Abdel-Rahman S.Z.
        • Sarker A.H.
        • Hang B.
        • Xie J.
        • Tomkinson A.E.
        • Zhou M.
        • Shen B.
        • Wang G.
        • Wu C.
        • Yu D.
        • et al.
        Increased risk of lung cancer associated with a functionally impaired polymorphic variant of the DNA glycosylase NEIL2.
        DNA Repair. 2012; 11: 570-578
        • Maiti A.K.
        • Boldogh I.
        • Spratt H.
        • Mitra S.
        • Hazra T.K.
        Mutator phenotype of mammalian cells due to deficiency of NEIL1 DNA glycosylase, an oxidized base-specific repair enzyme.
        DNA Repair. 2008; 7: 1213-1220
        • Todaro G.J.
        • Green H.
        Quantitative studies of the growth of mouse embryo cells in culture and their development into established lines.
        J. Cell Biol. 1963; 17: 299-313
        • Lee C.
        Protein extraction from mammalian tissues.
        Methods Mol. Biol. 2007; 362: 385-389
        • Santos J.H.
        • Meyer J.N.
        • Mandavilli B.S.
        • Van Houten B
        Quantitative PCR-based measurement of nuclear and mitochondrial DNA damage and repair in mammalian cells.
        Methods Mol. Biol. 2006; 314: 183-199
        • Chatterjee A.
        • Saha S.
        • Chakraborty A.
        • Silva-Fernandes A.
        • Mandal S.M.
        • Neves-Carvalho A.
        • Liu Y.
        • Pandita R.K.
        • Hegde M.L.
        • Hegde P.M.
        • Boldogh I.
        • Ashizawa T.
        • Koeppen A.H.
        • Pandita T.K.
        • Maciel P.
        • et al.
        The role of the mammalian DNA end-processing enzyme polynucleotide kinase 3′-phosphatase in spinocerebellar ataxia type 3 pathogenesis.
        PLoS Genet. 2015; 11e1004749
        • Suganya R.
        • Chakraborty A.
        • Miriyala S.
        • Hazra T.K.
        • Izumi T.
        Suppression of oxidative phosphorylation in mouse embryonic fibroblast cells deficient in apurinic/apyrimidinic endonuclease.
        DNA Repair. 2015; 27: 40-48
        • Ayala-Torres S.
        • Chen Y.
        • Svoboda T.
        • Rosenblatt J.
        • Van Houten B.
        Analysis of gene specific DNA damage and repair using quantitative polymerase chain reaction.
        Methods. 2000; 22: 135-147
        • Dignam J.D.
        • Lebovitz R.M.
        • Roeder R.G.
        Acute transcription initiation by RNA polymerase II in a soluble extract from isolated mammalian nuclei.
        Nucleic Acids Res. 1983; 11: 1475-1489
        • Kudrycki K.
        • Stein-Izsak C.
        • Behn C.
        • Grillo M.
        • Akeson R.
        • Margolis F.L.
        Olf-1-binding site: characterization of an olfactory neuron-specific promoter motif.
        Mol. Cell. Biol. 1993; 13: 3002-3014
        • Zhang J.
        • Ding X.
        Identification and characterization of a novel tissue-specific transcriptional activating element in the 5′-flanking region of the CYP2A3 gene predominantly expressed in rat olfactory mucosa.
        J. Biol. Chem. 1998; 273: 23454-23462
        • Aygün O.
        • Svejstrup J.
        • Liu Y.
        A RECQ5-RNA polymerase II association identified by targeted proteomic analysis of human chromatin.
        Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 8580-8584
        • Sailaja B.S.
        • Takizawa T.
        • Meshorer E.
        Chromatin immunoprecipitation in mouse hippocampal cells and tissues.
        Methods Mol. Biol. 2012; 809: 353-364
        • Das A.
        • Wiederhold L.
        • Leppard J.B.
        • Kedar P.
        • Prasad R.
        • Wang H.
        • Boldogh I.
        • Karimi-Busheri F.
        • Weinfeld M.
        • Tomkinson A.E.
        • Wilson S.H.
        • Mitra S.
        • Hazra T.K.
        NEIL2-initiated, APE-independent repair of oxidized bases in DNA: evidence for a repair complex in human cells.
        DNA Repair. 2006; 5: 1439-1448
        • Boldogh I.
        • Bacsi A.
        • Choudhury B.K.
        • Dharajiya N.
        • Alam R.
        • Hazra T.K.
        • Mitra S.
        • Goldblum R.M.
        • Sur S.
        ROS generated by pollen NADPH oxidase provide a signal that augments antigen-induced allergic airway inflammation.
        J. Clin. Invest. 2005; 115: 2169-2179
        • Bacsi A.
        • Aguilera-Aguirre L.
        • Szczesny B.
        • Radak Z.
        • Hazra T.K.
        • Sur S.
        • Ba X.
        • Boldogh I.
        Down-regulation of 8-oxoguanine DNA glycosylase 1 expression in the airway epithelium ameliorates allergic lung inflammation.
        DNA Repair. 2013; 12: 18-26
        • George S.H.
        • Gertsenstein M.
        • Vintersten K.
        • Korets-Smith E.
        • Murphy J.
        • Stevens M.E.
        • Haigh J.J.
        • Nagy A.
        Developmental and adult phenotyping directly from mutant embryonic stem cells.
        Proc. Natl. Acad. Sci. U.S.A. 2007; 104: 4455-4460
        • Lewandoski M.
        • Wassarman K.M.
        • Martin G.R.
        Zp3-cre, a transgenic mouse line for the activation or inactivation of loxP-flanked target genes specifically in the female germ line.
        Curr. Biol. 1997; 7: 148-151
        • Kawakami H.
        • Maruyama H.
        • Yasunami M.
        • Ohkubo H.
        • Hara H.
        • Saida T.
        • Nakanishi S.
        • Nakamura S.
        Cloning and expression of a rat brain basic helix-loop-helix factor.
        Biochem. Biophys. Res. Commun. 1996; 221: 199-204
        • Hart A.H.
        • Hartley L.
        • Ibrahim M.
        • Robb L.
        Identification, cloning and expression analysis of the pluripotency promoting Nanog genes in mouse and human.
        Dev. Dyn. 2004; 230: 187-198
        • Newton D.A.
        • Rao K.M.
        • Dluhy R.A.
        • Baatz J.E.
        Hemoglobin is expressed by alveolar epithelial cells.
        J. Biol. Chem. 2006; 281: 5668-5676
        • Wiederhold L.
        • Leppard J.B.
        • Kedar P.
        • Karimi-Busheri F.
        • Rasouli-Nia A.
        • Weinfeld M.
        • Tomkinson A.E.
        • Izumi T.
        • Prasad R.
        • Wilson S.H.
        • Mitra S.
        • Hazra T.K.
        AP endonuclease-independent DNA base excision repair in human cells.
        Mol. Cell. 2004; 15: 209-220
        • Hunt C.R.
        • Dix D.J.
        • Sharma G.G.
        • Pandita R.K.
        • Gupta A.
        • Funk M.
        • Pandita T.K.
        Genomic instability and enhanced radiosensitivity in Hsp70.1- and Hsp70.3-deficient mice.
        Mol. Cell. Biol. 2004; 24: 899-911
        • Pandita R.K.
        • Sharma G.G.
        • Laszlo A.
        • Hopkins K.M.
        • Davey S.
        • Chakhparonian M.
        • Gupta A.
        • Wellinger R.J.
        • Zhang J.
        • Powell S.N.
        • Roti Roti J.L.
        • Lieberman H.B.
        • Pandita T.K.
        Mammalian Rad9 plays a role in telomere stability, S- and G2-phase-specific cell survival, and homologous recombinational repair.
        Mol. Cell. Biol. 2006; 26: 1850-1864
        • Pandita R.K.
        • Chow T.T.
        • Udayakumar D.
        • Bain A.L.
        • Cubeddu L.
        • Hunt C.R.
        • Shi W.
        • Horikoshi N.
        • Zhao Y.
        • Wright W.E.
        • Khanna K.K.
        • Shay J.W.
        • Pandita T.K.
        Single-strand DNA-binding protein SSB1 facilitates TERT recruitment to telomeres and maintains telomere G-overhangs.
        Cancer Res. 2015; 75: 858-869
        • Mabley J.G.
        • Pacher P.
        • Deb A.
        • Wallace R.
        • Elder R.H.
        • Szabó C.
        Potential role for 8-oxoguanine DNA glycosylase in regulating inflammation.
        FASEB J. 2005; 19: 290-292
        • Aguilera-Aguirre L.
        • Bacsi A.
        • Radak Z.
        • Hazra T.K.
        • Mitra S.
        • Sur S.
        • Brasier A.R.
        • Ba X.
        • Boldogh I.
        Innate inflammation induced by the 8-oxoguanine DNA glycosylase-1-KRAS-NF-κB pathway.
        J. Immunol. 2014; 193: 4643-4653
        • Li G.
        • Yuan K.
        • Yan C.
        • Fox 3rd, J.
        • Gaid M.
        • Breitwieser W.
        • Bansal A.K.
        • Zeng H.
        • Gao H.
        • Wu M.
        8-Oxoguanine-DNA glycosylase 1 deficiency modifies allergic airway inflammation by regulating STAT6 and IL-4 in cells and in mice.
        Free Radic. Biol. Med. 2012; 52: 392-401
        • Bacsi A.
        • Chodaczek G.
        • Hazra T.K.
        • Konkel D.
        • Boldogh I.
        Increased ROS generation in subsets of OGG1 knockout fibroblast cells.
        Mech. Ageing Dev. 2007; 128: 637-649
        • Ba X.
        • Bacsi A.
        • Luo J.
        • Aguilera-Aguirre L.
        • Zeng X.
        • Radak Z.
        • Brasier A.R.
        • Boldogh I.
        8-Oxoguanine DNA glycosylase-1 augments proinflammatory gene expression by facilitating the recruitment of site-specific transcription factors.
        J. Immunol. 2014; 192: 2384-2394
        • Brasier A.R.
        The NF-κB regulatory network.
        Cardiovasc. Toxicol. 2006; 6: 111-130
        • Das A.
        • Hazra T.K.
        • Boldogh I.
        • Mitra S.
        • Bhakat K.K.
        Induction of the human oxidized base-specific DNA glycosylase NEIL1 by reactive oxygen species.
        J. Biol. Chem. 2005; 280: 35272-35280
        • Klungland A.
        • Rosewell I.
        • Hollenbach S.
        • Larsen E.
        • Daly G.
        • Epe B.
        • Seeberg E.
        • Lindahl T.
        • Barnes D.E.
        Accumulation of premutagenic DNA lesions in mice defective in removal of oxidative base damage.
        Proc. Natl. Acad. Sci. U.S.A. 1999; 96: 13300-13305
        • Ocampo M.T.
        • Chaung W.
        • Marenstein D.R.
        • Chan M.K.
        • Altamirano A.
        • Basu A.K.
        • Boorstein R.J.
        • Cunningham R.P.
        • Teebor G.W.
        Targeted deletion of mNth1 reveals a novel DNA repair enzyme activity.
        Mol. Cell. Biol. 2002; 22: 6111-6121
        • Vartanian V.
        • Lowell B.
        • Minko I.G.
        • Wood T.G.
        • Ceci J.D.
        • George S.
        • Ballinger S.W.
        • Corless C.L.
        • McCullough A.K.
        • Lloyd R.S.
        The metabolic syndrome resulting from a knockout of the NEIL1 DNA glycosylase.
        Proc. Natl. Acad. Sci. U.S.A. 2006; 103: 1864-1869
        • Torisu K.
        • Tsuchimoto D.
        • Ohnishi Y.
        • Nakabeppu Y.
        Hematopoietic tissue-specific expression of mouse Neil3 for endonuclease VIII-like protein.
        J. Biochem. 2005; 138: 763-772
        • Gu H.
        • Marth J.D.
        • Orban P.C.
        • Mossmann H.
        • Rajewsky K.
        Deletion of a DNA polymerase β gene segment in T cells using cell type-specific gene targeting.
        Science. 1994; 265: 103-106
        • Sugo N.
        • Aratani Y.
        • Nagashima Y.
        • Kubota Y.
        • Koyama H.
        Neonatal lethality with abnormal neurogenesis in mice deficient in DNA polymerase β.
        EMBO J. 2000; 19: 1397-1404
        • Izumi T.
        • Brown D.B.
        • Naidu C.V.
        • Bhakat K.K.
        • Macinnes M.A.
        • Saito H.
        • Chen D.J.
        • Mitra S.
        Two essential but distinct functions of the mammalian abasic endonuclease.
        Proc. Natl. Acad. Sci. U.S.A. 2005; 102: 5739-5743
        • Puebla-Osorio N.
        • Lacey D.B.
        • Alt F.W.
        • Zhu C.
        Early embryonic lethality due to targeted inactivation of DNA ligase III.
        Mol. Cell. Biol. 2006; 26: 3935-3941
        • Reis A.M.
        • Mills W.K.
        • Ramachandran I.
        • Friedberg E.C.
        • Thompson D.
        • Queimado L.
        Targeted detection of in vivo endogenous DNA base damage reveals preferential base excision repair in the transcribed strand.
        Nucleic Acids Res. 2012; 40: 206-219
        • Guo J.
        • Hanawalt P.C.
        • Spivak G.
        Comet-FISH with strand-specific probes reveals transcription coupled repair of 8-oxoguanine in human cells.
        Nucleic Acids Res. 2013; 41: 7700-7712
        • Sarker A.H.
        • Tsutakawa S.E.
        • Kostek S.
        • Ng C.
        • Shin D.S.
        • Peris M.
        • Campeau E.
        • Tainer J.A.
        • Nogales E.
        • Cooper P.K.
        Recognition of RNA polymerase II and transcription bubbles by XPG, CSB, and TFIIH: insights for transcription-coupled repair and Cockayne syndrome.
        Mol. Cell. 2005; 20: 187-198
        • Selby C.P.
        • Sancar A.
        Cockayne syndrome group B protein enhances elongation by RNA polymerase II.
        Proc. Natl. Acad. Sci. U.S.A. 1997; 94: 11205-11209
        • Tantin D.
        • Kansal A.
        • Carey M.
        Recruitment of the putative transcription-repair coupling factor CSB/ERCC6 to RNA polymerase II elongation complexes.
        Mol. Cell. Biol. 1997; 17: 6803-6814
        • Vallabhaneni H.
        • O'Callaghan N.
        • Sidorova J.
        • Liu Y.
        Defective repair of oxidative base lesions by the DNA glycosylase Nth1 associates with multiple telomere defects.
        PLoS Genet. 2013; 9e1003639
        • Wang Z.
        • Rhee D.B.
        • Lu J.
        • Bohr C.T.
        • Zhou F.
        • Vallabhaneni H.
        • de Souza-Pinto N.C.
        • Liu Y.
        Characterization of oxidative guanine damage and repair in mammalian telomeres.
        PLoS Genet. 2010; 6e1000951
        • Bah A.
        • Azzalin C.M.
        The telomeric transcriptome: from fission yeast to mammals.
        Int. J. Biochem. Cell Biol. 2012; 44: 1055-1059
        • Porro A.
        • Feuerhahn S.
        • Delafontaine J.
        • Riethman H.
        • Rougemont J.
        • Lingner J.
        Functional characterization of the TERRA transcriptome at damaged telomeres.
        Nat. Commun. 2014; 55379
        • Liao B.Y.
        • Zhang J.
        Null mutations in human and mouse orthologs frequently result in different phenotypes.
        Proc. Natl. Acad. Sci. U.S.A. 2008; 105: 6987-6992
        • Cooke M.S.
        • Evans M.D.
        • Dizdaroglu M.
        • Lunec J.
        Oxidative DNA damage: mechanisms, mutation, and disease.
        FASEB J. 2003; 17: 1195-1214
        • Arai T.
        • Kelly V.P.
        • Minowa O.
        • Noda T.
        • Nishimura S.
        The study using wild-type and Ogg1 knockout mice exposed to potassium bromate shows no tumor induction despite an extensive accumulation of 8-hydroxyguanine in kidney DNA.
        Toxicology. 2006; 221: 179-186
        • Osorio A.
        • Milne R.L.
        • Kuchenbaecker K.
        • Vaclová T.
        • Pita G.
        • Alonso R.
        • Peterlongo P.
        • Blanco I.
        • de la Hoya M.
        • Duran M.
        • Díez O.
        • Ramon Y.C.
        • Konstantopoulou I.
        • Martínez-Bouzas C.
        • Andrés Conejero R.
        • et al.
        DNA glycosylases involved in base excision repair may be associated with cancer risk in BRCA1 and BRCA2 mutation carriers.
        PLoS Genet. 2014; 10e1004256
        • Nijland R.
        • Hofland T.
        • van Strijp J.A.
        Recognition of LPS by TLR4: potential for antiinflammatory therapies.
        Mar. Drugs. 2014; 12: 4260-4273
        • da Silva Correia J.
        • Soldau K.
        • Christen U.
        • Tobias P.S.
        • Ulevitch R.J.
        Lipopolysaccharide is in close proximity to each of the proteins in its membrane receptor complex. Transfer from CD14 to TLR4 and MD-2.
        J. Biol. Chem. 2001; 276: 21129-21135
        • Jamaluddin M.
        • Wang S.
        • Boldogh I.
        • Tian B.
        • Brasier A.R.
        TNF-α-induced NF-κB/RelA Ser (276) phosphorylation and enhanceosome formation is mediated by an ROS-dependent PKAc pathway.
        Cell. Signal. 2007; 19: 1419-1433
        • Choudhary S.
        • Kalita M.
        • Fang L.
        • Patel K.V.
        • Tian B.
        • Zhao Y.
        • Edeh C.B.
        • Brasier A.R.
        Inducible tumor necrosis factor (TNF) receptor-associated factor-1 expression couples the canonical to the non-canonical NFκB pathway in TNF stimulation.
        J. Biol. Chem. 2013; 288: 14612-14623
        • Tian B.
        • Nowak D.E.
        • Brasier A.R.
        A TNF-induced gene expression program under oscillatory NF-κB control.
        BMC Genomics. 2005; 6: 137
        • Balkwill F.
        • Mantovani A.
        Inflammation and cancer: back to Virchow?.
        Lancet. 2001; 357: 539-545
        • Hanahan D.
        • Weinberg R.A.
        Hallmarks of cancer: the next generation.
        Cell. 2011; 144: 646-674
        • Calvo J.A.
        • Meira L.B.
        • Lee C.Y.
        • Moroski-Erkul C.A.
        • Abolhassani N.
        • Taghizadeh K.
        • Eichinger L.W.
        • Muthupalani S.
        • Nordstrand L.M.
        • Klungland A.
        • Samson L.D.
        DNA repair is indispensable for survival after acute inflammation.
        J. Clin. Invest. 2012; 122: 2680-2689
        • Zhai X.
        • Zhao H.
        • Liu Z.
        • Wang L.E.
        • El-Naggar A.K.
        • Sturgis E.M.
        • Wei Q.
        Functional variants of the NEIL1 and NEIL2 genes and risk and progression of squamous cell carcinoma of the oral cavity and oropharynx.
        Clin. Cancer Res. 2008; 14: 4345-4352