Synthetic lethal analysis implicates Ste20p, a p21-activated potein kinase, in polarisome activation.
The p21-activated kinases Ste20p and Cla4p carry out undefined functions that are essential for viability during budding in Saccharomyces cerevisiae. To gain insight into the roles of Ste20p, we have used a synthetic lethal mutant screen to identify additional genes that are required in the absence of Cla4p. Altogether, we identified 65 genes, including genes with roles in cell polarity, mitosis, and cell wall maintenance. Herein, we focus on a set that defines a function carried out by Bni1p and several of its interacting proteins. We found that Bni1p and a group of proteins that complex with Bni1p (Bud6p, Spa2p, and Pea2p) are essential in a cla4delta mutant background. Bni1p, Bud6p, Spa2, and Pea2p are members of a group of polarity determining proteins referred to as the polarisome. Loss of polarisome proteins from a cla4delta strain causes cells to form elongated buds that have mislocalized septin rings. In contrast, other proteins that interact with or functionally associate with Bni1p and have roles in nuclear migration and cytokinesis, including Num1p and Hof1p, are not essential in the absence of Cla4p. Finally, we have found that Bni1p is phosphorylated in vivo, and a substantial portion of this phosphorylation is dependent on STE20. Together, these results suggest that one function of Ste20p may be to activate the polarisome complex by phosphorylation of Bni1p.
Goehring
April S
AS
Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403-1229, USA.
Mitchell
David A
DA
Tong
Amy Hin Yan
AH
Keniry
Megan E
ME
Boone
Charles
C
Sprague
George F
GF
D001483:Base Sequence; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D016764:Cell Polarity; D003598:Cytoskeletal Proteins; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism
C107727:BUD6 protein, S cerevisiae; C105191:Bni1 protein, S cerevisiae; D003598:Cytoskeletal Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins; C102138:PEA2 protein, S cerevisiae; C065889:SPA2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae