Mec1 Modulates Interhomolog Crossover and Interplays with Tel1 at Post Double-Strand Break Stages

During meiosis I, programmed DNA double-strand breaks (DSBs) occur to promote chromosome pairing and recombination between homologs. In Saccharomyces cerevisiae, Mec1 and Tel1, the orthologs of human ATR and ATM, respectively, regulate events upstream of the cell cycle checkpoint to initiate DNA repair. Tel1(ATM) and Mec1(ATR) are required for phosphorylating various meiotic proteins during recombination. This study aimed to investigate the role of Tel1(ATM) and Mec1(ATR) in meiotic prophase via physical analysis of recombination. Tel1(ATM) cooperated with Mec1(ATR) to mediate DSB-to-single end invasion transition, but negatively regulated DSB formation. Furthermore, Mec1(ATR) was required for the formation of interhomolog joint molecules from early prophase, thus establishing a recombination partner choice. Moreover, Mec1(ATR) specifically promoted crossover-fated DSB repair. Together, these results suggest that Tel1(ATM) and Mec1(ATR) function redundantly or independently in all post-DSB stages.