HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 282, Issue 6, 3465-3477, February 9, 2007

This Article Full Text Full Text (PDF) All Versions of this Article: 282/6/3465    most recent M606582200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Singh, P. Articles by Shen, B. Search for Related Content PubMed PubMed Citation Articles by Singh, P. Articles by Shen, B. Social Bookmarking                      What's this?

Concerted Action of Exonuclease and Gap-dependent Endonuclease Activities of FEN-1 Contributes to the Resolution of Triplet Repeat Sequences (CTG)_n- and (GAA)_n-derived Secondary Structures Formed during Maturation of Okazaki Fragments^*

From the Department of Radiation Biology, City of Hope National Medical Center and Beckman Research Institute, Duarte, California 91010

There is much evidence to indicate that FEN-1 efficiently cleaves single-stranded DNA flaps but is unable to process double-stranded flaps or flaps adopting secondary structures. However, the absence of Fen1 in yeast results in a significant increase in trinucleotide repeat (TNR) expansion. There are then two possibilities. One is that TNRs do not always form stable secondary structures or that FEN-1 has an alternative approach to resolve the secondary structures. In the present study, we test the hypothesis that concerted action of exonuclease and gap-dependent endonuclease activities of FEN-1 play a role in the resolution of secondary structures formed by (CTG)_n and (GAA)_n repeats. Employing a yeast FEN-1 mutant, E176A, which is deficient in exonuclease (EXO) and gap endonuclease (GEN) activities but retains almost all of its flap endonuclease (FEN) activity, we show severe defects in the cleavage of various TNR intermediate substrates. Precise knock-in of this point mutation causes an increase in both the expansion and fragility of a (CTG)_n tract in vivo. Taken together, our biochemical and genetic analyses suggest that although FEN activity is important for single-stranded flap processing, EXO and GEN activities may contribute to the resolution of structured flaps. A model is presented to explain how the concerted action of EXO and GEN activities may contribute to resolving structured flaps, thereby preventing their expansion in the genome.

Received for publication, July 11, 2006 , and in revised form, November 27, 2006.

^* This study was funded by National Institutes of Health Grants RO1 CA085344 and RO1 CA073764 (to B. S.). 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.

¹ To whom correspondence should be addressed: Dept. of Radiation Biology, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA 91010. Tel.: 626-301-8879; Fax: 626-301-8280; E-mail: bshen{at}coh.org.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				I.-t. Cho, D.-h. Kim, Y.-H. Kang, C.-H. Lee, T. Amangyelid, T. A. Nguyen, J. Hurwitz, and Y.-S. Seo Human Replication Factor C Stimulates Flap Endonuclease 1 J. Biol. Chem., April 17, 2009; 284(16): 10387 - 10399. [Abstract] [Full Text] [PDF]

				G.-F. Richard, A. Kerrest, and B. Dujon Comparative Genomics and Molecular Dynamics of DNA Repeats in Eukaryotes Microbiol. Mol. Biol. Rev., December 1, 2008; 72(4): 686 - 727. [Abstract] [Full Text] [PDF]

				P. Singh, M. Yang, H. Dai, D. Yu, Q. Huang, W. Tan, K. H. Kernstine, D. Lin, and B. Shen Overexpression and Hypomethylation of Flap Endonuclease 1 Gene in Breast and Other Cancers Mol. Cancer Res., November 1, 2008; 6(11): 1710 - 1717. [Abstract] [Full Text] [PDF]

				P. Liu, L. Qian, J.-S. Sung, N. C. de Souza-Pinto, L. Zheng, D. F. Bogenhagen, V. A. Bohr, D. M. Wilson III, B. Shen, and B. Demple Removal of Oxidative DNA Damage via FEN1-Dependent Long-Patch Base Excision Repair in Human Cell Mitochondria Mol. Cell. Biol., August 15, 2008; 28(16): 4975 - 4987. [Abstract] [Full Text] [PDF]

				Z. Guo, L. Qian, R. Liu, H. Dai, M. Zhou, L. Zheng, and B. Shen Nucleolar Localization and Dynamic Roles of Flap Endonuclease 1 in Ribosomal DNA Replication and Damage Repair Mol. Cell. Biol., July 1, 2008; 28(13): 4310 - 4319. [Abstract] [Full Text] [PDF]