Polo-like kinase Cdc5 orchestrates Cdk1 regulation via Swe1 and Mih1 during meiotic prophase I exit

Meiotic recombination defects activate a checkpoint that delays meiotic prophase I exit in budding yeast by inhibiting Ndt80-dependent expression of the cyclin CLB1 and the polo-like kinase CDC5. Additionally, Swe1-mediated inhibitory phosphorylation of Cdk1/Cdc28 on tyrosine 19 reinforces this arrest. Following checkpoint release, meiosis I entry depends on removal of inhibitory phosphorylation controlled by the opposing activities of Swe1 and the Mih1 phosphatase. Here, we define how this regulatory network is rewired at the prophase I-meiosis I transition. We show that Swe1 is required for checkpoint maintenance but not activation. We further demonstrate that Cdc5 promotes Cdk1 activation by inducing Swe1 degradation and facilitating Mih1 nuclear translocation. Unlike in mitosis, Swe1 degradation by Cdc5 does not require CDK priming and can occur upon artificial colocalization. These findings uncover an additional role for Cdc5 in promoting meiotic cell cycle progression, highlighting how conserved cell cycle regulators are adapted to drive meiosis. The polo-like kinase Cdc5 activates Cdk1 to drive entry into meiosis I in budding yeast by promoting Swe1 degradation and Mih1 nuclear translocation, revealing how conserved cell-cycle regulators are rewired to control meiotic progression.