title: Linkage of replication to start by the Cdk inhibitor Sic1.
abstract: In Saccharomyces cerevisiae, three G1 cyclins (Clns) are important for Start, the event committing cells to division. Sic1, an inhibitor of C1b-Cdc28 kinases, became phosphorylated at Start, and this phosphorylation depended on the activity of Clns. Sic1 was subsequently lost, which depended on the activity of Clns and the ubiquitin-conjugating enzyme Cdc34. Inactivation of Sic1 was the only nonredundant essential function of Clns, because a sic1 deletion rescued the inviability of the cln1 cln2 cln3 triple mutant. In sic1 mutants, DNA replication became uncoupled from budding. Thus, Sic1 may be a substrate of Cln-Cdc28 complexes, and phosphorylation and proteolysis of Sic1 may regulate commitment to replication at Start.
authors.affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Schneider
authors.forename: Q H
authors.initials: QH
authors.lastname: Yang
authors.forename: A B
authors.initials: AB
authors.lastname: Futcher
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D017489:CDC28 Protein Kinase, S cerevisiae / Q000037:antagonists & inhibitors / Q000378:metabolism; D002453:Cell Cycle; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins / Q000378:metabolism; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D008025:Ligases / Q000378:metabolism; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases
chemical_list: D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins; D004271:DNA, Fungal; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C577449:CDC34 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D017489:CDC28 Protein Kinase, S cerevisiae; D008025:Ligases