Hsl7p, a negative regulator of Ste20p protein kinase in the Saccharomyces cerevisiae filamentous growth-signaling pathway.
In the budding yeast, Saccharomyces cerevisiae, protein kinases Ste20p (p21(Cdc42p/Rac)-activated kinase), Ste11p [mitogen-activated protein kinase (MAPK) kinase kinase], Ste7p (MAPK kinase), Fus3p, and Kss1p (MAPKs) are utilized for haploid mating, invasive growth, and diploid filamentous growth. Members of the highly conserved Ste20p/p65(PAK) protein kinase family regulate MAPK signal transduction pathways from yeast to man. We describe here a potent negative regulator of Ste20p in the yeast filamentous growth-signaling pathway. We identified a mutant, hsl7, that exhibits filamentous growth on rich medium. Hsl7p belongs to a highly conserved protein family in eukaryotes. Hsl7p associates with the noncatalytic region within the amino-terminal half of Ste20p as well as Cdc42p. Deletions of HSL7 in haploid and diploid strains led to cell elongation and enhancement of both haploid invasive growth and diploid pseudohyphal growth. However, deletions of STE20 in haploid and diploid greatly diminished these hsl7-associated phenotypes. In addition, overexpression of HSL7 inhibited pseudohyphal growth. Thus, Hsl7p may inhibit the activity of Ste20p in the S. cerevisiae filamentous growth-signaling pathway. Our genetic analyses suggest the possibility that Cdc42p and Hsl7p compete for binding to Ste20p for pseudohyphal development when starved for nitrogen.
National Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, 1-1 Higashi, Tsukuba 305-8566, Japan. atushi@nibh.go.jp
A
A
Fujita
A
A
Tonouchi
T
T
Hiroko
F
F
Inose
T
T
Nagashima
R
R
Satoh
S
S
Tanaka
D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics; D019204:GTP-Binding Proteins / Q000378:metabolism; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction / Q000235:genetics*; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D019204:GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae