Role of the yeast Gin4p protein kinase in septin assembly and the relationship between septin assembly and septin function.
To identify septin-interacting proteins in Saccharomyces cerevisiae, we screened for mutations that are synthetically lethal with a cdc12 septin mutation. One of the genes identified was GIN4, which encodes a protein kinase related to Hsl1p/Nik1p and Ycl024Wp in S. cerevisiae and to Nim1p/Cdr1p and Cdr2p in Schizosaccharomyces pombe. The Gin4p kinase domain displayed a two-hybrid interaction with the COOH-terminal portion of the Cdc3p septin, and Gin4p colocalized with the septins at the mother-bud neck. This localization depended on the septins and on the COOH-terminal (nonkinase) region of Gin4p, and overproduction of this COOH-terminal region led to a loss of septin organization and associated morphogenetic defects. We detected no effect of deleting YCL024W, either alone or in combination with deletion of GIN4. Deletion of GIN4 was not lethal but led to a striking reorganization of the septins accompanied by morphogenetic abnormalities and a defect in cell separation; however, remarkably, cytokinesis appeared to occur efficiently. Two other proteins that localize to the neck in a septin-dependent manner showed similar reorganizations and also appeared to remain largely functional. The septin organization observed in gin4Delta vegetative cells resembles that seen normally in cells responding to mating pheromone, and no Gin4p was detected in association with the septins in such cells. The organization of the septins observed in gin4Delta cells and in cells responding to pheromone appears to support some aspects of the model for septin organization suggested previously by Field et al. (Field, C.M., O. Al-Awar, J. Rosenblatt, M.L. Wong, B. Alberts, and T.J. Mitchison. 1996. J. Cell Biol. 133:605-616).
Longtine
M S
MS
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Fares
H
H
Pringle
J R
JR
D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans; D018797:Cell Cycle Proteins / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins / Q000378:metabolism; D015870:Gene Expression; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009693:Nucleic Acid Hybridization; D051304:Profilins; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid
C099504:CDC12 protein, S cerevisiae; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; D051304:Profilins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C490133:cdc3 protein, S pombe; D011494:Protein Kinases; C107283:GIN4 protein, S cerevisiae; D018844:Cyclin-Dependent Kinases; D020928:Mitogen-Activated Protein Kinases; C072724:SLT2 protein, S cerevisiae