In most eukaryotes, commitment to cell division occurs in late G1 phase at an event called Start in the yeast Saccharomyces cerevisiae, and called the restriction point in mammalian cells. Start is triggered by the cyclin-dependent kinase Cdc28 and three rate-limiting activators, the G1 cyclins Cln1, Cln2 and Cln3. Cyclin accumulation in G1 is driven in part by the cell-cycle-regulated transcription of CLN1 and CLN2, which peaks at Start. CLN transcription is modulated by physiological signals that regulate G1 progression, but it is unclear whether Cln protein stability is cell-cycle-regulated. It has been suggested that once cells pass Start, Cln proteolysis is triggered by the mitotic cyclins Clb1, 2, 3 and 4. But here we show that G1 cyclins are unstable in G1 phase, and that Clb-Cdc28 activity is not needed fgr G1 cyclin turnover. Cln instability thus provides a means to couple Cln-Cdc28 activity to transcriptional regulation and protein synthetic rate in pre-Start G1 cells.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|