title: Budding yeast PAK kinases regulate mitotic exit by two different mechanisms.
abstract: We report the characterization of the dominant-negative CLA4t allele of the budding yeast CLA4 gene, encoding a member of the p21-activated kinase (PAK) family of protein kinases, which, together with its homologue STE20, plays an essential role in promoting budding and cytokinesis. Overproduction of the Cla4t protein likely inhibits both endogenous Cla4 and Ste20 and causes a delay in the onset of anaphase that correlates with inactivation of Cdc20/anaphase-promoting complex (APC)-dependent proteolysis of both the cyclinB Clb2 and securin. Although the precise mechanism of APC inhibition by Cla4t remains to be elucidated, our results suggest that Cla4 and Ste20 may regulate the first wave of cyclinB proteolysis mediated by Cdc20/APC, which has been shown to be crucial for activation of the mitotic exit network (MEN). We show that the Cdk1-inhibitory kinase Swe1 is required for the Cla4t-dependent delay in cell cycle progression, suggesting that it might be required to prevent full Cdc20/APC and MEN activation. In addition, inhibition of PAK kinases by Cla4t prevents mitotic exit also by a Swe1-independent mechanism impinging directly on the MEN activator Tem1.
authors.affiliation: Dipartimento di Biotecnologie e Bioscienze, Piazza della Scienza 2, 20126 Milano, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Chiroli
authors.forename: Roberta
authors.initials: R
authors.lastname: Fraschini
authors.forename: Alessia
authors.initials: A
authors.lastname: Beretta
authors.forename: Mariagrazia
authors.initials: M
authors.lastname: Tonelli
authors.forename: Giovanna
authors.initials: G
authors.lastname: Lucchini
authors.forename: Simonetta
authors.initials: S
authors.lastname: Piatti
mesh_terms: D000705:Anaphase / Q000502:physiology; D064173:Anaphase-Promoting Complex-Cyclosome; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D018816:Genes, cdc / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins; D008025:Ligases / Q000235:genetics / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases; D008938:Mitosis / Q000235:genetics*; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D064249:Securin; D043743:Ubiquitin-Protein Ligase Complexes
chemical_list: D018797:Cell Cycle Proteins; D019926:Cyclin B; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; C578004:PDS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D064249:Securin; C089965:TEM1 protein, S cerevisiae; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D020559:Monomeric GTP-Binding Proteins; D008025:Ligases