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Dna2 removes toxic RPA-ssDNA flaps generated from meiotic recombination-associated DNA synthesis

ABSTRACT: During the repair of DNA double-strand breaks (DSBs), de novo synthesized DNA strand can displace the parental strand to generate single-strand DNA (ssDNA) flaps. Many programmed DSBs and thus many ssDNA flaps occur during meiosis. However, how these flaps are removed remains enigmatic. Here, we show that meiosis-specific depletion of Dna2 (dna2-md) in Saccharomyces cerevisiae causes an abundant accumulation of RPA-ssDNA flaps and an expansion of RPA from DSBs to broader regions. As a result, DSB repair is defective and spores are inviable, although the levels of crossovers/non-crossovers seem to be unaffected. Furthermore, inducing Dna2 expression at pachytene is highly effective in removing accumulated RPA and restoring spore viability. Moreover, the depletion of Pif1, an activator of polymerase δ required for meiotic recombination-associated DNA synthesis, and Pif1 inhibitor Mlh2 decreased and increased RPA accumulation in dna2-md, respectively. Together, our findings show that meiotic DSB repair requires Dna2 to remove RPA-ssDNA flaps generated from meiotic recombination-associated DNA synthesis. Additionally, we showed that Dna2 also regulates DSB-independent RPA distribution.

ORGANISM(S): Saccharomyces cerevisiae SK1

PROVIDER: GSE217628 | GEO | 2023/08/30

REPOSITORIES: GEO

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Project description:DNA double-strand breaks (DSBs) initiate meiotic recombination. Past DSB-mapping studies have used rad50S or sae2? mutants, which are defective in break processing, to accumulate DSBs, and report large (= 50 kb) “DSB-hot” regions that are separated by “DSB-cold” domains of similar size. Substantial recombination occurs in some DSB-cold regions, suggesting that DSB patterns are not normal in rad50S or sae2? mutants. We therefore developed novel methods that detect DSBs using ssDNA enrichment and microarray hybridization, and that use background-based normalization to allow cross-comparison between array datasets, to map genome-wide the DSBs that accumulate in processing-capable, repair-defective dmc1î and dmc1î rad51î mutants. DSBs were observed at known hotspots, but also in most previously-identified “DSB-cold” regions, including near centromeres and telomeres. While about 40% of the genome is DSB-cold in rad50S mutants, analysis of meiotic ssDNA from dmc1? shows that most of these regions have significant DSB activity. Thus, DSBs are distributed much more uniformly than was previously believed. Southern-blot assays of DSBs in selected regions in dmc1?, rad50S and wild-type cells confirm these findings. Comparisons of DSB signals in dmc1, dmc1 rad51, and dmc1 spo11 mutant strains identify Dmc1 as the primary strand transfer activity genome-wide, and Spo11-induced lesions as initiating all meiotic recombination. Keywords: DSB mapping, ChIP-chip, single strand DNA , BND cellulose We use two different strategies to map the genome-wide distribution of meiotic DSBs in the yeast Saccharomyces cerevisiae. The first is a chromatin immunoprecipitation (ChIP) based approach that targets the Spo11p protein, which remains covalently attached to DSB ends in the rad50S mutant background. The second approach involves BND cellulose enrichment of the single strand DNA (ssDNA) recombination intermediate formed by end-resection at DSB sites following Spo11p removal. We use dmc1 and dmc1 rad51 mutants that accumulates meiotic single strand DNA intermediates

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Dna2 removes toxic RPA-ssDNA flaps generated from meiotic recombination-associated DNA synthesis

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