title: Regulation of cell polarity through phosphorylation of Bni4 by Pho85 G1 cyclin-dependent kinases in Saccharomyces cerevisiae.
abstract: In the budding yeast Saccharomyces cerevisiae, the G1-specific cyclin-dependent kinases (Cdks) Cln1,2-Cdc28 and Pcl1,2-Pho85 are essential for ensuring that DNA replication and cell division are properly linked to cell polarity and bud morphogenesis. However, the redundancy of Cdks and cyclins means that identification of relevant Cdk substrates remains a significant challenge. We used array-based genetic screens (synthetic genetic array or SGA analysis) to dissect redundant pathways associated with G1 cyclins and identified Bni4 as a substrate of the Pcl1- and Pcl2-Pho85 kinases. BNI4 encodes an adaptor protein that targets several proteins to the bud neck. Deletion of BNI4 results in severe growth defects in the absence of the Cdc28 cyclins Cln1 and Cln2, and overexpression of BNI4 is toxic in yeast cells lacking the Pho85 cyclins Pcl1 and Pcl2. Phosphorylation of Bni4 by Pcl-Pho85 is necessary for its localization to the bud neck, and the bud neck structure can be disrupted by overexpressing BNI4 in pcl1Deltapcl2Delta mutant cells. Our data suggest that misregulated Bni4 may bind in an uncontrolled manner to an essential component that resides at the bud neck, causing catastrophic morphogenesis defects.
authors.affiliation: Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 3E1, Canada.
authors.forename: Jian
authors.initials: J
authors.lastname: Zou
authors.forename: Helena
authors.initials: H
authors.lastname: Friesen
authors.forename: Jennifer
authors.initials: J
authors.lastname: Larson
authors.forename: Dongqing
authors.initials: D
authors.lastname: Huang
authors.forename: Mike
authors.initials: M
authors.lastname: Cox
authors.forename: Kelly
authors.initials: K
authors.lastname: Tatchell
authors.forename: Brenda
authors.initials: B
authors.lastname: Andrews
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism*; D016764:Cell Polarity; D056746:Cyclin G; D018844:Cyclin-Dependent Kinases / Q000302:isolation & purification / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D005800:Genes, Fungal; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000302:isolation & purification / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C494956:Bni4p protein, S cerevisiae; D018797:Cell Cycle Proteins; D056746:Cyclin G; D016213:Cyclins; C090559:PCL2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C070839:PCL1 protein, S cerevisiae; D018844:Cyclin-Dependent Kinases; C058605:PHO85 protein, S cerevisiae