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ATM and PRDM9 Regulate SPO11-bound Recombination Intermediates During Meiosis

ABSTRACT: Meiotic recombination is initiated by genome-wide SPO11-induced double-strand breaks (DSBs) that are processed by MRE11-mediated release of SPO11-bound oligonucleotides (SPO11-oligos). The DSB is then resected and loaded with DMC1/RAD51 filaments that invade homologous chromosome templates. In most mammals, DSB locations (“hotspots”) are determined by the DNA sequence specificity of the PRDM9 DNA binding zinc finger array. Here, we demonstrate the first direct detection of meiotic DSBs in vertebrates by performing END-seq on mouse spermatocytes using low sample input. We find that DMC1 limits both the minimum and maximum length of ssDNA produced at all hotspots, whereas 53BP1, BRCA1 and EXO1 play a surprisingly minimal role in meiotic resection. Through enzymatic modifications to the END-seq protocol that mimic the in vivo processing of SPO11, we identify a novel meiotic recombination intermediate (RI) with SPO11 still bound to the 3’ end via a small stretch of dsDNA (“SPO11-RI”) that is dependent on the presence of PRDM9. We propose that SPO11-RI is generated because chromatin-bound PRDM9 blocks MRE11 from releasing SPO11 via 3’-5’ resection. SPO11-RI is present at all hotspots and correlates with the localization and frequency of crossovers and noncrossovers. In Atm–/– spermatocytes, multiple DSBs at the same hotspot reduces SPO11-RI formation, while unresected DNA-bound SPO11 accumulates because of defective MRE11 initiation. Thus in addition to their global roles in governing SPO11 breakage, ATM and PRDM9 are critical local regulators of mammalian SPO11 processing.

ORGANISM(S): Mus musculus

PROVIDER: GSE138915 | GEO | 2020/02/20

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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ATM and PRDM9 Regulate SPO11-bound Recombination Intermediates During Meiosis

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