Authors

B. Y. Lee; A. Morano; A. Porcellini;M. T. Muller

Comments

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Abbreviated Journal Title

Nucleic Acids Res.

Keywords

DOUBLE-STRAND BREAKS; MAMMALIAN-CELLS; GENOTOXIC STRESS; GENE; CONVERSION; EXCISION-REPAIR; DEMETHYLATION; DAMAGE; RECOMBINATION; INDUCTION; PROTEIN; Biochemistry & Molecular Biology

Abstract

In this work, we examine regulation of DNA methyltransferase 1 (DNMT1) by the DNA damage inducible protein, GADD45 alpha. We used a system to induce homologous recombination (HR) at a unique double-strand DNA break in a GFP reporter in mammalian cells. After HR, the repaired DNA is hypermethylated in recombinant clones showing low GFP expression (HR-L expressor class), while in high expressor recombinants (HR-H clones) previous methylation patterns are erased. GADD45 alpha, which is transiently induced by double-strand breaks, binds to chromatin undergoing HR repair. Ectopic overexpression of GADD45 alpha during repair increases the HR-H fraction of cells (hypomethylated repaired DNA), without altering the recombination frequency. Conversely, silencing of GADD45 alpha increases methylation of the recombined segment and amplifies the HR-L expressor (hypermethylated) population. GADD45 alpha specifically interacts with the catalytic site of DNMT1 and inhibits methylation activity in vitro. We propose that double-strand DNA damage and the resulting HR process involves precise, strand selected DNA methylation by DNMT1 that is regulated by GADD45 alpha. Since GADD45 alpha binds with high avidity to hemimethylated DNA intermediates, it may also provide a barrier to spreading of methylation during or after HR repair.

Journal Title

Nucleic Acids Research

Volume

40

Issue/Number

6

Publication Date

1-1-2012

Document Type

Article

Language

English

First Page

2481

Last Page

2493

WOS Identifier

WOS:000302312400017

ISSN

0305-1048

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