Swi5 controls a novel wave of cyclin synthesis in late mitosis.
We have shown previously that the Swi5 transcription factor regulates the expression of the SIC1 Cdk inhibitor in late mitosis. This suggests that Swi5 might control other genes with roles in ending mitosis. We identified a gene with a Swi5-binding site in the promoter that encoded a protein with high homology to Pcl2, a cyclin-like protein that associates with the Cdk Pho85. This gene, PCL9, is indeed regulated by Swi5 in late M phase, the only cyclin known to be expressed at this point in the cell cycle. The Pcl9 protein is associated with a Pho85-dependent protein kinase activity, and the protein is unstable with peak levels occurring in late M phase. PCL2 is already known to be expressed in late G1 and we find that, in addition, it is also regulated by Swi5 in telophase. The expression of PCL2 and PCL9 at this stage of the cell cycle implies a role for the Pho85 Cdk at the end of mitosis. Consistent with this a synthetic interaction was observed between pho85delta and strains deleted for SIC1, SWI5, and SPO12. These and other studies support the notion that the M/G1 switch is a major cell cycle transition.
Aerne
B L
BL
Division of Yeast Genetics, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom.
Johnson
A L
AL
Toyn
J H
JH
Johnston
L H
LH
D001665:Binding Sites; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D008938:Mitosis; D011401:Promoter Regions, Genetic; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics* / Q000378:metabolism
D018797:Cell Cycle Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C090559:PCL2 protein, S cerevisiae; C081540:SBF protein, S cerevisiae; C086926:SIC1 protein, S cerevisiae; C080218:SWI5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D018844:Cyclin-Dependent Kinases; C058605:PHO85 protein, S cerevisiae