Abstract
Budding yeast Pch2 protein is a widely conserved meiosis-specific protein whose role is implicated in the control of formation and displacement of meiotic crossover events. In contrast to previous studies where the function of Pch2 was implicated in the steps after meiotic double-strand breaks (DSBs) are formed, we present evidence that Pch2 is involved in meiotic DSB formation, the initiation step of meiotic recombination. The reduction of DSB formation caused by the pch2 mutation is most prominent in the sae2 mutant background, whereas the impact remains mild in the rad51 dmc1 double mutant background. The DSB reduction is further pronounced when pch2 is combined with a hypomorphic allele of SPO11. Interestingly, the level of DSB reduction is highly variable between chromosomes, with minimal impact on small chromosomes VI and III. We propose a model in which Pch2 ensures efficient formation of meiotic DSBs which is necessary for igniting the subsequent meiotic checkpoint responses that lead to proper differentiation of meiotic recombinants.
Highlights
Meiosis plays a central role in sexually reproducing organisms by producing haploid gametes from diploid parental cells [1]
We considered the possibility that the pch2 mutation might bypass the cell cycle arrest of various recombination mutants by reducing meiotic double-strand breaks (DSBs) formation, the initiator of meiotic recombination
The efficiency of DSB formation in a given chromosome was evaluated by using pulsed-field gel electrophoresis (PFGE), followed by Southern blotting with probes recognizing the ends of specific chromosomes
Summary
Meiosis plays a central role in sexually reproducing organisms by producing haploid gametes from diploid parental cells [1]. A single round of DNA replication is followed by two successive rounds of nuclear division, meiosis I and meiosis II respectively. Homologous chromosomes segregate in meiosis I whereas, in meiosis II, sister chromatids are separated like mitosis. During prophase of meiosis I, homologous recombination is highly induced and plays two essential roles [2]. Recombination ensures that each chromosome finds its homologous partner. A subset of recombination events are resolved as crossovers, establishing physical connections between homologs. These crossovers are essential for ensuring the proper alignment of chromosomes on the spindle apparatus, and their faithful segregation at meiosis I
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