Salagean, A. | bioRxiv Science

bioRxiv2022

BRCA1/BRC-1 and SMC-5/6 regulate DNA repair pathway engagement during C. elegans meiosis

The preservation of genome integrity during sperm and egg development is vital for reproductive success. During meiosis, the tumor suppressor BRCA1/BRC-1 and structural maintenance of chromosomes 5/6 (SMC-5/6) complex genetically interact to promote high fidelity DNA double strand break (DSB) repair, but the specific DSB repair outcomes these proteins regulate remain unknown. Here we show that BRCA1/BRC-1 and the SMC-5/6 complex limit intersister crossover recombination as well as error-prone repair pathways during meiotic prophase I. Using genetic and cytological methods to monitor repair of DSBs with different repair partners in Caenorhabditis elegans, we demonstrate that both BRC-1 and SMC-5/6 repress intersister crossover recombination events, with meiotic cells becoming more dependent upon these proteins to repair DSBs in late meiotic prophase I. Sequencing of conversion tracts from homolog-independent DSB repair events indicates that BRC-1 regulates intersister/intrachromatid noncrossover conversion tract length. Moreover, we find that BRC-1 also specifically inhibits error prone repair of DSBs induced at mid-pachytene. Finally, we reveal that functional BRC-1 enhances DSB repair defects in smc-5 mutants by repressing theta-mediated end joining (TMEJ). Taken together, our study illuminates the coordinate interplay of BRC-1 and SMC-5/6 to regulate DSB repair outcomes in the germline.

genetics↗

bioRxiv2020

Sister chromatid repair maintains genomic integrity during meiosis in Caenorhabditis elegans

During meiosis, the maintenance of genome integrity is critical for generating viable haploid gametes [1]. In meiotic prophase I, double-strand DNA breaks (DSBs) are induced and a subset of these DSBs are repaired as interhomolog crossovers to ensure proper chromosome segregation. DSBs in excess of the permitted number of crossovers must be repaired by other pathways to ensure genome integrity [2]. To determine if the sister chromatid is engaged for meiotic DSB repair during oogenesis, we developed an assay to detect sister chromatid repair events at a defined DSB site during Caenorhabditis elegans meiosis. Using this assay, we directly demonstrate that the sister chromatid is available as a meiotic repair template for both crossover and noncrossover recombination, with noncrossovers being the predominant recombination outcome. We additionally find that the sister chromatid is the exclusive recombination partner for DSBs during late meiotic prophase I. Analysis of noncrossover conversion tract sequences reveals that DSBs are processed similarly throughout prophase I and recombination intermediates remain central around the DSB site. Further, we demonstrate that the SMC-5/6 complex is required for long conversion tracts in early prophase I and intersister crossovers during late meiotic prophase I; whereas, the XPF-1 nuclease is required only in late prophase to promote sister chromatid repair. In response to exogenous DNA damage at different stages of meiosis, we find that mutants for SMC-5/6 and XPF-1 have differential effects on progeny viability. Overall, we propose that SMC-5/6 both processes recombination intermediates and promotes sister chromatid repair within meiotic prophase I, while XPF-1 is required as an intersister resolvase only in late prophase I.

genetics↗