E2F1 Regulates the Base Excision Repair Gene XRCC1 and Promotes DNA Repair*
- Department of Medicine, Division of Hematology and Medical Oncology, Oregon Health and Science University, Portland, Oregon 97239
- 3 To whom correspondence should be addressed: Dept. of Medicine, Division of Hematology and Medical Oncology, Mail Code: L586B, Oregon Health and Science University, 3181 S.W. Sam Jackson Park Rd., Portland, OR 97239. Tel.: 503-494-8321; Fax: 503-418-0844; E-mail: lopezc{at}ohsu.edu.
Abstract
The E2F1 transcription factor activates S-phase-promoting genes, mediates apoptosis, and stimulates DNA repair through incompletely understood mechanisms. XRCC1 (x-ray repair cross-complementing group 1) protein is important for efficient single strand break/base excision repair. Although both damage and proliferative signals increase XRCC1 levels, the mechanisms regulating XRCC1 transcription remain unclear. To study these upstream mechanisms, the XRCC1 promoter was cloned into a luciferase reporter. Ectopic expression of wild-type E2F1, but not an inactive mutant E2F1(132E), activated the XRCC1 promoter-luciferase reporter, and deletion of predicted E2F1 binding sites in the promoter attenuated E2F1-induced activation. Endogenous XRCC1 expression increased in cells conditionally expressing wild-type, but not mutant E2F1, and methyl methanesulfonate-induced DNA damage stimulated XRCC1 expression in E2F1+/+ but not E2F1-/- mouse embryo fibroblasts (MEFs). Additionally, E2F1-/- MEFs displayed attenuated DNA repair after methyl methanesulfonate-induced damage compared with E2F1+/+ MEFs. Moreover, Chinese hamster ovary cells with mutant XRCC1 (EM9) were more sensitive to E2F1-induced apoptosis compared with Chinese hamster ovary cells with wild-type XRCC1 (AA8). These results provide new mechanistic insight into the role of the E2F pathway in maintaining genomic stability.
Footnotes
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↵4 The abbreviations used are: SSB, single strand break; SSBR, single strand break repair; BER, base excision repair; IP, immunoprecipitation; MEF, mouse embryo fibroblast; FITC, fluorescein isothiocyanate; MMS, methyl methanesulfonate; GFP, green fluorescent protein.
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↵* This work was supported, in whole or in part, by National Institutes of Health, Grant CA104997 (to C. D. L.). This work was also supported by the Oregon Health and Science University Division of Hematology and Medical Oncology and the Oregon Health and Science University Cancer Institute. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 Present address: Dept. of Medicine, Beijing You An Hospital, Capital University of Medical Sciences, Beijing 100054, China.
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↵2 Present address: Dept. of Surgery, Shandong Tumor Hospital, Jinan Shandong 250117, China.
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- Received December 18, 2008.
- Revision received March 12, 2008.
- The American Society for Biochemistry and Molecular Biology, Inc.
