ATM and ATR Influence Meiotic Crossover Formation Through Antagonistic and Overlapping Functions inC. elegans

ABSTRACT During meiosis, formation of double-strand breaks (DSBs) and repair by homologous recombination between homologs creates crossovers (COs) that facilitate chromosome segregation. CO formation is tightly regulated to ensure the integrity of this process. The DNA damage response kinases, Ataxia-telangiectasia mutated (ATM) and RAD3-related (ATR) have emerged as key regulators of CO formation in yeast, flies, and mice, influencing DSB formation, repair pathway choice, and cell cycle progression. The molecular networks that ATM and ATR influence during meiosis are still being resolved in other organisms. Here we show that Caenorhabditis elegans ATM and ATR homologs, ATM-1 and ATL-1 respectively, act at multiple steps in CO formation to ultimately ensure that COs are formed on all chromosomes. We show a role for ATM-1 in regulating the choice of repair template, biasing use of the homologous chromosome instead of the sister chromatid. Our data suggests a model in which ATM-1 and ATL-1 have antagonistic roles in very early repair processing, but are redundantly required for accumulation of the RAD-51 recombinase at DSB sites. We propose that these features of ATM-1 and ATL-1 ensure both CO formation on all chromosomes and accurate repair of additional DSBs. Article Summary Crossovers formed during meiosis connect homologs and properly align them for cell division. The central importance of crossovers is underscored by the existence of extensive regulatory processes that ensures the proper execution of these events. This paper explores the evolutionary conserved roles of the central DNA damage response kinases, ATM and ATR, in crossover formation. The authors show that these kinases function together as rheostats to promote timely formation of crossovers on all chromosomes but to limit extensive DNA damage. This work provides a platform for identifying conserved meiotic targets of ATM and ATR that affect fertility across species.