INO80-dependent chromatin remodeling regulates early and late stages of mitotic homologous recombination
Journal
DNA Repair
Journal Volume
8
Journal Issue
3
Pages
360-369
Date Issued
2009
Author(s)
Abstract
Chromatin remodeling is emerging as a critical regulator of DNA repair factor access to DNA damage, and optimum accessibility of these factors is a major determinant of DNA repair outcome. Hence, chromatin remodeling is likely to play a key role in genome stabilization and tumor suppression. We previously showed that nucleosome eviction near double-strand breaks (DSBs) in yeast is regulated by the INO80 nucleosome remodeling complex and is defective in mutants lacking the Arp8 subunit of INO80. In the absence of homologous donor sequences, RPA recruitment to a DSB appeared normal in arp8£G, but Rad51 recruitment was defective. We now show that the early strand invasion step of homologous recombination (HR) is markedly delayed in an arp8£G haploid, but there is only a minor defect in haploid HR efficiency (MAT switching). In an arp8£G diploid, interhomolog DSB repair by HR shows a modest defect that is partially suppressed by overexpression of Rad51 or its mediator, Rad52. In wild type cells, DSB repair typically results in gene conversion, and most gene conversion tracts are continuous, reflecting efficient mismatch repair of heteroduplex DNA. In contrast, arp8£G gene conversion tracts are longer and frequently discontinuous, indicating defects in late stages of HR. Interestingly, when a homologous donor sequence is present, Rad51 is recruited normally to a DSB in arp8£G, but its transfer to the donor is delayed, and this correlates with defective displacement of donor nucleosomes. We propose that retained nucleosomes at donors destabilize heteroduplex DNA or impair mismatch recognition, reflected in delayed strand invasion and altered conversion tracts. ? 2008 Elsevier B.V. All rights reserved.
Subjects
Double-strand break repair
Gene conversion
Histones
Rad51
RPA
Type
journal article