DNA damage response clamp loader Rad24(Rad17) and Mec1(ATR) kinase have distinct functions in regulating meiotic crossovers
AbstractCrossover (CO) recombination is essential for chromosome segregation during meiosis I. The number and distribution of COs are tightly regulated during meiosis. CO control includes CO assurance and CO interference, which guarantee at least one CO per a bivalent and evenly-spaced CO distribution, respectively. Previous studies showed the role of DNA damage response (DDR) clamp and its loader in efficient formation of meiotic COs by promoting the recruitment of a pro-CO protein Zip3 and interhomolog recombination, and also by suppressing ectopic recombination. In this study, by classical tetrad analysis ofSaccharomyces cerevisiae, we showed that a mutant defective in theRAD24 gene(RAD17in other organisms), which encodes the DDR clamp loader, displayed reduced CO frequencies on two shorter chromosomes (IIIandV) but not on a long chromosome (chromosomeVII). The residual COs in therad24mutant do not show interference. In contrast to therad24mutant, mutants defective in the ATR kinase homolog Mec1/Esr1, including amec1null and amec1kinase-dead mutant, show little or no defect in CO frequency. On the other hand,mec1COs show defects in interference, similar to therad24mutant. Moreover, CO formation and its control are implemented in a chromosome-specific manner, which may reflect a role for chromosome size in regulation.