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RecG Directs DNA Synthesis during Double-Strand Break Repair.

Authors :
Azeroglu B
Mawer JS
Cockram CA
White MA
Hasan AM
Filatenkova M
Leach DR
Source :
PLoS genetics [PLoS Genet] 2016 Feb 12; Vol. 12 (2), pp. e1005799. Date of Electronic Publication: 2016 Feb 12 (Print Publication: 2016).
Publication Year :
2016

Abstract

Homologous recombination provides a mechanism of DNA double-strand break repair (DSBR) that requires an intact, homologous template for DNA synthesis. When DNA synthesis associated with DSBR is convergent, the broken DNA strands are replaced and repair is accurate. However, if divergent DNA synthesis is established, over-replication of flanking DNA may occur with deleterious consequences. The RecG protein of Escherichia coli is a helicase and translocase that can re-model 3-way and 4-way DNA structures such as replication forks and Holliday junctions. However, the primary role of RecG in live cells has remained elusive. Here we show that, in the absence of RecG, attempted DSBR is accompanied by divergent DNA replication at the site of an induced chromosomal DNA double-strand break. Furthermore, DNA double-stand ends are generated in a recG mutant at sites known to block replication forks. These double-strand ends, also trigger DSBR and the divergent DNA replication characteristic of this mutant, which can explain over-replication of the terminus region of the chromosome. The loss of DNA associated with unwinding joint molecules previously observed in the absence of RuvAB and RecG, is suppressed by a helicase deficient PriA mutation (priA300), arguing that the action of RecG ensures that PriA is bound correctly on D-loops to direct DNA replication rather than to unwind joint molecules. This has led us to put forward a revised model of homologous recombination in which the re-modelling of branched intermediates by RecG plays a fundamental role in directing DNA synthesis and thus maintaining genomic stability.

Details

Language :
English
ISSN :
1553-7404
Volume :
12
Issue :
2
Database :
MEDLINE
Journal :
PLoS genetics
Publication Type :
Academic Journal
Accession number :
26872352
Full Text :
https://doi.org/10.1371/journal.pgen.1005799