Late-G1 cyclin-CDK activity is essential for control of cell morphogenesis in budding yeast.
The accurate spatial and temporal coordination of cell polarization with DNA replication and segregation guarantees the fidelity of genetic transmission. Here we report that in Saccharomyces cerevisiae, a build-up or burst of G1 cyclin-dependent kinase (CDK) activity through activation of the cyclin genes CLN1,2 and PCL1,2 is essential for cell morphogenesis, but not for other events associated with the G1-S-phase transition, including DNA replication. Strains lacking a burst of late-G1 cyclin-CDK activity (LG1C(-)) undergo a catastrophic morphogenesis and halt the nuclear cycle at the morphogenesis checkpoint in G2 phase. Consistent with a role in morphogenesis, the Pho85 G1 cyclins Pcl1 and Pcl2 show a unique pattern of localization to sites of polarized cell growth, and strains lacking PCL1 and PCL2 show genetic interactions with the cell polarity GTPase Cdc42, its regulators and downstream effectors. Our data suggest that inability to assemble a septin ring and localize the GTP exchange factor Cdc24 at the incipient bud site may be the primary morphogenetic defects in LG1C-depleted cells. We conclude that a burst of late G1 cyclin-CDK activity is essential for establishing cell polarity and development of the cleavage apparatus.
Moffat
Jason
J
Department of Medical Genetics & Microbiology, University of Toronto, 1 Kings College Circle, Rm. 4287, Medical Sciences Building, Toronto, Ontario, M5S 1A8, Canada.
Andrews
Brenda
B
D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D016764:Cell Polarity / Q000235:genetics*; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication / Q000235:genetics; D016193:G1 Phase / Q000235:genetics; D016195:G2 Phase / Q000235:genetics; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors; D009024:Morphogenesis / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
C073594:CDC24 protein, S cerevisiae; D018797:Cell Cycle Proteins; D016213:Cyclins; D020662:Guanine Nucleotide Exchange Factors; C090559:PCL2 protein, S cerevisiae; D011518:Proto-Oncogene Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C070839:PCL1 protein, S cerevisiae; D018844:Cyclin-Dependent Kinases; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae