Meiotic DNA break resection and recombination rely on chromatin remodeler Fun30

Abstract

AbstractDNA double-strand breaks (DSBs) are nucleolytically processed to generate single-stranded DNA tails for homologous recombination. InSaccharomyces cerevisiaemeiosis, this 5’-to-3’ resection involves initial nicking by the Mre11–Rad50–Xrs2 complex (MRX) plus Sae2, then exonucleolytic digestion by Exo1. Chromatin remodeling adjacent to meiotic DSBs is thought to be necessary for resection, but the relevant remodeling activity was unknown. Here we show that the SWI/SNF-like ATPase Fun30 plays a major, non-redundant role in resecting meiotic DSBs. Afun30null mutation shortened resection tract lengths almost as severely as anexo1-nd(nuclease-dead) mutation, and resection was further shortened in thefun30 exo1-nddouble mutant. Fun30 associates with chromatin in response to meiotic DSBs, and the constitutive positioning of nucleosomes governs resection endpoint locations in the absence of Fun30. We infer that Fun30 directly promotes both the MRX- and Exo1-dependent steps in resection, possibly by removing nucleosomes from broken chromatids. Moreover, we found that the extremely short resection in thefun30 exo1-nddouble mutant is accompanied by compromised interhomolog recombination bias, leading to defects in recombination and chromosome segregation. Thus, this study also provides insight about the minimal resection lengths needed for robust recombination.