Phosphorylation of the septin cdc3 in g1 by the cdc28 kinase is essential for efficient septin ring disassembly.
The septins constitute a family of filament-forming proteins ubiquitous in eukaryotic species. We demonstrate here that the Saccharomyces cerevisiae septin, Cdc3, is a substrate of the cell cycle regulatory cyclin-dependent kinase (Cdk), Cdc28. Two serines near the C-terminus of Cdc3 are phosphorylated in a Cdc28-dependent manner. Analysis of a mutant allele that cannot be phosphorylated at these sites revealed an effect of Cdc28 phosphorylation of Cdc3 at the time of budding. Immunofluorescence analysis of wild-type and mutant Cdc3 indicated that prevention of phosphorylation at Cdc28-dependent sites impairs the disassembly of the old septin ring, which is inherited at mitosis but which usually disappears immediately prior to assembly of a new ring. Furthermore, immuno-fluorescence analysis of septin ring dynamics in a G1 cyclin (Cln) mutant suggests that G1 cyclin function is required for efficient ring disassembly. Thus, phosphorylation of Cdc3 by the Cdc28 kinase at the end of G1 may facilitate initiation of a new cell cycle by promoting disassembly of the obsolete septin ring from the previous cell cycle.
Tang
Carol S L
CS
The Scripps Research Institute, Department of Molecular Biology, MB-7, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Reed
Steven I
SI
D000595:Amino Acid Sequence; D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010766:Phosphorylation; D051304:Profilins; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013997:Time Factors
C086662:CDC3 protein, S cerevisiae; C082719:CLN1 protein, S cerevisiae; C082721:CLN2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D016213:Cyclins; D005656:Fungal Proteins; D051304:Profilins; D029701:Saccharomyces cerevisiae Proteins; D017489:CDC28 Protein Kinase, S cerevisiae