ATM and PRDM9 Regulate SPO11-bound Recombination Intermediates During Meiosis

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. END-seq and ChIP-seq data used to study meiotic double strand breaks