Phosphorylation of the RecQ Helicase Sgs1/BLM Controls Its DNA Unwinding Activity during Meiosis and Mitosis.

The Bloom's helicase ortholog, Sgs1, orchestrates the formation and disengagement of recombination intermediates to enable controlled crossing-over during meiotic and mitotic DNA repair. Whether its enzymatic activity is temporally regulated to implement formation of noncrossovers prior to the activation of crossover-nucleases is unknown. Here, we show that, akin to the ...
Mus81-Mms4, Yen1, and MutL?-Exo1 nucleases, Sgs1 helicase function is under cell-cycle control through the actions of CDK and Cdc5 kinases. Notably, however, whereas CDK and Cdc5 unleash nuclease function during M phase, they act in concert to stimulate Sgs1 activity during S phase/prophase I. Mechanistically, CDK-mediated phosphorylation enhances the velocity and processivity of Sgs1, which stimulates DNA unwinding in vitro and joint molecule processing in vivo. Subsequent hyper-phosphorylation by Cdc5 appears to reduce the activity of Sgs1, while activating Mus81-Mms4 and MutL?-Exo1. These findings suggest a concerted mechanism driving orderly formation of noncrossover and crossover recombinants in meiotic and mitotic cells.
Mesh Terms:
Cell Cycle Proteins, DNA, Fungal, Homologous Recombination, Meiosis, Mitosis, Phosphorylation, Protein Processing, Post-Translational, Protein Serine-Threonine Kinases, RecQ Helicases, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Dev Cell
Date: Dec. 22, 2019
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