title: Genes that can bypass the CLN requirement for Saccharomyces cerevisiae cell cycle START.
abstract: Cell cycle START in Saccharomyces cerevisiae requires at least one of the three CLN genes (CLN1, CLN2, or CLN3). A total of 12 mutations bypassing this requirement were found to be dominant mutations in a single gene that we named BYC1 (for bypass of CLN requirement). We also isolated a plasmid that had cln bypass activity at a low copy number; the gene responsible was distinct from BYC1 and was identical to the recently described BCK2 gene. Strains carrying bck2::ARG4 disruption alleles were fully viable, but bck2::ARG4 completely suppressed the cln bypass activity of BYC1. swi4 and swi6 deletion alleles also efficiently suppressed BYC1 cln bypass activity; Swi4 and Swi6 are components of a transcription factor previously implicated in control of CLN1 and CLN2 expression. bck2::ARG4 was synthetically lethal with cln3 deletion, suggesting that CLN1 and CLN2 cannot function in the simultaneous absence of BCK2 and CLN3; this observation correlates with low expression of CLN1 and CLN2 in bck2 strains deprived of CLN3 function. Thus, factors implicated in CLN1 and CLN2 expression and/or function are also required for BYC1 function in the absence of all three CLN genes; this may suggest the involvement of other targets of Swi4, Swi6, and Bck2 in START.
authors.affiliation: Rockefeller University, New York, New York 10021.
authors.forename: C B
authors.initials: CB
authors.lastname: Epstein
authors.forename: F R
authors.initials: FR
authors.lastname: Cross
mesh_terms: D002453:Cell Cycle; D003001:Cloning, Molecular; D016213:Cyclins / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics* / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D005799:Genes, Dominant; D005800:Genes, Fungal; D005804:Genes, Lethal; D016153:Genes, Suppressor; D047908:Intracellular Signaling Peptides and Proteins; D016254:Mutagenesis, Insertional; D010750:Phosphoproteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: C082733:BCK2 protein, S cerevisiae; C082719:CLN1 protein, S cerevisiae; C082721:CLN2 protein, S cerevisiae; C079895:CLN3 protein, S cerevisiae; D016213:Cyclins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors