Protein phosphatase 1 in association with Bud14 inhibits mitotic exit in Saccharomyces cerevisiae

Abstract

Mitotic exit in budding yeast is dependent on correct orientation of the mitotic spindle along the cell polarity axis. When accurate positioning of the spindle fails, a surveillance mechanism named the Spindle Position Checkpoint (SPOC) prevents cells from exiting mitosis. Mutants with a defective SPOC become multinucleated and lose their genomic integrity. Yet, a comprehensive understanding of the SPOC mechanism is missing. In this study, we identified the type 1 protein phosphatase, Glc7, in association with its regulatory protein Bud14 as a novel checkpoint component. We further showed that Glc7-Bud14 promotes dephosphorylation of the SPOC effector protein Bfa1. Our results suggest a model in which two mechanisms act in parallel for a robust checkpoint response: first, the SPOC kinase Kin4 isolates Bfa1 away from the inhibitory kinase Cdc5 and second, Glc7-Bud14 dephosphorylates Bfa1 to fully activate the checkpoint effector.

Functional genomic analysis of Candida albicans protein kinases reveals modulators of morphogenesis in diverse environments

“…In S. cerevisiae , deletion of genes encoding key components of the spindle position checkpoint, including Kin4, Bub2, and Bud14, leads to premature exit from mitosis and accumulation of multinucleate cells. 32 , 44 , 45 Indeed, deletion of orf19.3751 in C. albicans resulted in many multinucleated cellular compartments, consistent with a role of this kinase in regulating the MEN. While filamentation induced by cell-cycle arrest signals through the cAMP-PKA pathway, a central hub for morphogenetic signaling in C. albicans , the downstream transcription factors important for mediating this transition can differ.…”

SWR1 chromatin remodeling complex prevents mitotic slippage during spindle position checkpoint arrest

“…For this, we used temperature-sensitive MEN mutants (men-ts). The lack of mitotic exit inhibitors, such as Bfa1-Bub2, Bud14-Glc7, or Mck1, rescues the growth defect of men-ts mutants at their semipermissive temperature ( Kocakaplan et al. , 2021 ; Rathi et al.…”

“…Bmh1 promotes removal of Bfa1-Bub2 GAP complexes from SPBs to prevent inactivation of Bfa1 by the polo-like kinase Cdc5 in cells with misaligned spindles ( Caydasi et al. , 2014 ), whereas PP1 (Glc7) in complex with Bud14 promotes dephosphorylation of Cdc5-phosphorylated Bfa1 ( Kocakaplan et al. , 2021 ).…”

The budding yeast GSK-3 homologue Mck1 is an essential component of the spindle position checkpoint

“…In the absence of FEAR, Bfa1 phosphorylation by Kin4 is dispensable to hold mitotic arrest upon spindle misalignment suggesting that mechanisms in addition to Kin4 link spindle orientation to MEN regulation [ 42 , 46 ]. Recently, it was described that the dephosphorylation of Bfa1 by the Glc7-Bud14 kinase complex serves as Kin4-independent mechanism to keep Bfa1–Bub2 active in cells with misaligned anaphase spindles by counteracting Cdc5 phosphorylation [ 45 ]. However, whether spindle orientation defects can feed directly into maintaining M-Cdk activity in addition to the regulation of Bfa1–Bub2 or MEN signalling remains an open question.…”

“…Recent studies provided evidence of a Kin4-independent pathway that holds the SPOC arrest parallel to the established Kin4-dependent regulation [43][44][45]. In the absence of FEAR, Bfa1 phosphorylation by Kin4 is dispensable to hold mitotic arrest upon spindle misalignment suggesting that mechanisms in addition to Kin4 link spindle orientation to MEN regulation [42,46].…”