title: Requirements and reasons for effective inhibition of the anaphase promoting complex activator CDH1.
abstract: Anaphase promoting complex (APC)-Cdh1 targets multiple mitotic proteins for degradation upon exit from mitosis into G1; inhibitory phosphorylation of Cdh1 by cyclin-dependent kinase (CDK) and Polo kinase has been proposed to prevent the premature degradation of substrates in the ensuing cell cycle. Here, we demonstrate essentiality of CDK phosphorylation of Cdh1 in Saccharomyces cerevisiae by exact endogenous gene replacement of CDH1 with CDK-unphosphorylatable CDH1-m11; in contrast, neither Cdh1 polo kinase sites nor polo interaction motifs are required. CDH1-m11 cells arrest in the first cycle with replicated DNA and sustained polarized growth; most cells have monopolar spindles. Blocking proteolysis of the Cin8 kinesin in CDH1-m11 cells does not promote spindle pole body (SPB) separation. In contrast, expression of undegradable mitotic cyclin results in both SPB separation and the restoration of isotropic growth. A minority of CDH1-m11 cells arrest with short bipolar spindles that fail to progress to anaphase; this can be accounted for by a failure to accumulate Cdc20 and consequent failure to cleave cohesin. Bipolar spindle assembly in CDH1-m11 cells is strikingly sensitive to gene dosage of the stoichiometric Cdh1 inhibitor ACM1. Thus, different spindle-regulatory pathways have distinct sensitivities to Cdh1, and ACM1 may buffer essential CDK phosphorylation of Cdh1.
authors.affiliation: The Rockefeller University, New York, NY 10065, USA.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Robbins
authors.forename: Frederick R
authors.initials: FR
authors.lastname: Cross
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D064200:Cdh1 Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D016547:Kinesins; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism*
chemical_list: C516306:Acm1 protein, S cerevisiae; C577583:CDH1 protein, S cerevisiae; C075342:CIN8 protein, S cerevisiae; D064200:Cdh1 Proteins; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; C081927:CDC5 protein, S cerevisiae; D018844:Cyclin-Dependent Kinases; D016547:Kinesins