title: The transcription factor Swi4 is target for PKA regulation of cell size at the G1 to S transition in Saccharomyces cerevisiae.
abstract: To investigate the specific target of PKA in the regulation of cell cycle progression and cell size we developed a new approach using the yeast strain GG104 bearing a deletion in adenylate cyclase gene and permeable to cAMP ( cyr1Δ, pde2Δ, msn2Δ, msn4Δ). In this strain the PKA activity is absent and can be activated by addition of cAMP in the medium, without any other change of the growth conditions. In the present work we show that the activation of PKA by exogenous cAMP in the GG104 strain exponentially growing in glucose medium caused a marked increase of cell size and perturbation of cell cycle with a transient arrest of cells in G1, followed by an accumulation of cells in G2/M phase with a minimal change in the growth rate. Deletion of CLN1 gene, but not of CLN2, abolished the transient G1 phase arrest. Consistently we found that PKA activation caused a transcriptional repression of CLN1 gene. Transcription of CLN1 is controlled by SBF and MBF dual-regulated promoter. We found that also the deletion of SWI4 gene abolished the transient G1 arrest suggesting that Swi4 is a target responsible for PKA modulation of G1/S phase transition. We generated a SWI4 allele mutated in the consensus site for PKA (Swi4(S159A)) and we found that expression of Swi4(S159A) protein in the GG104-Swi4Δ strain did not restore the transient G1 arrest induced by PKA activation, suggesting that Swi4 phosphorylation by PKA regulates CLN1 gene expression and G1/S phase transition.
authors.affiliation: a Dipartimento di Biotecnologie e Bioscienze ; Università di Milano Bicocca ; Milano , Italy.
authors.forename: Loredana
authors.initials: L
authors.lastname: Amigoni
authors.forename: Sonia
authors.initials: S
authors.lastname: Colombo
authors.forename: Fiorella
authors.initials: F
authors.lastname: Belotti
authors.forename: Lilia
authors.initials: L
authors.lastname: Alberghina
authors.forename: Enzo
authors.initials: E
authors.lastname: Martegani
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D048429:Cell Size; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D016193:G1 Phase / Q000235:genetics; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C082719:CLN1 protein, S cerevisiae; D016213:Cyclins; D004268:DNA-Binding Proteins; C062214:SWI4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases
keywords: Cln1; Cyclic AMP; G1 cyclins; Mitosis; SBF; budding yeast