PP21Cdc55 phosphatase imposes phosphothreonine-specific ordering of cell cycle phosphorylation

ABSTRACT: In the quantitative model for cell cycle control, progression from G1 through S phase and into mitosis is ordered by thresholds of increasing cyclin-dependent kinase (Cdk) activity. How such thresholds are read out by substrates, that respond with the correct phosphorylation timing, if not known. In budding yeast, Cdk phosphorylates its many substrates with widely varying efficiencies, but there is no obvious correlation between phosphorylation efficiency and timing. Instead, we explore here whether Cdk-counteracting phosphatases impose Cdk thresholds. We find that the abundant PP2ACdc55 phosphatase counteracts Cdk phosphorylation in interphase and delays phosphorylation of late Cdk substrates, an effect that is independent of its known impact on the Cdk tyrosine phosphorylation status. Strikingly, PP2ACdc55 specifically counteracts phosphorylation of threonine residues. Consequently, we find that threonine-directed phosphorylation occurs late in the cell cycle, compared to serine phosphorylation. Late phosphorylation of Ndd1, a model substrate, depends on threonine identity. Our results support a model in which phosphatases contribute to ordering cell cycle progression by directly counteracting Cdk phosphorylation and unveil a principle of cell cycle control based on the phosphoacceptor amino acid.

INSTRUMENT(S):

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Andrew Jones  

LAB HEAD: Ambrosius Snijders

PROVIDER: PXD004461 | Pride | 2017-01-23

REPOSITORIES: Pride