title: Phosphoregulation of Cbk1 is critical for RAM network control of transcription and morphogenesis.
abstract: The budding yeast regulation of Ace2 and morphogenesis (RAM) network integrates cell fate determination and morphogenesis. Its disruption impairs polarized growth and causes mislocalization of the transcription factor Ace2, resulting in failure of daughter cell-specific transcription required for cell separation. We find that phosphoregulation of the conserved AGC family kinase Cbk1 is critical for RAM network function. Intramolecular autophosphorylation of the enzyme's activation loop is critical for kinase activity but is only partially required for cell separation and polarized growth. In marked contrast, phosphorylation of a C-terminal hydrophobic motif is required for Cbk1 function in vivo but not for its kinase activity, suggesting a previously unappreciated level of control for this family of kinases. Phosphorylation of the C-terminal site is regulated over the cell cycle and requires the transcription factor Ace2 as well as all RAM network components. Therefore, Ace2 is not only a downstream target of Cbk1 but also reinforces activation of its upstream regulator.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Jaclyn M
authors.initials: JM
authors.lastname: Jansen
authors.forename: Margaret F
authors.initials: MF
authors.lastname: Barry
authors.forename: Charles K
authors.initials: CK
authors.lastname: Yoo
authors.forename: Eric L
authors.initials: EL
authors.lastname: Weiss
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D047908:Intracellular Signaling Peptides and Proteins; D008954:Models, Biological; D009024:Morphogenesis; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C066778:ACE2 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D010770:Phosphotransferases; C423362:CBK1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases