The SLT2 (MPK1) MAP kinase homolog is involved in polarized cell growth in Saccharomyces cerevisiae.
Bud emergence, spindle pole body duplication and DNA replication are all dependent on the activation of the CDC28 protein kinase at the Start point in the G1 phase of the cell cycle. Bud emergence requires polarization of the cytoskeleton and secretory vesicles to a specific site on the cell surface. Cdc28p activated by G1-cyclins triggers polarization of actin to the site of bud emergence and favors apical bud growth (Lew, D. J., and S. I. Reed. 1993. J. Cell Biol. 120:1305-1320). We isolated slt2-1 as a mutation that enhances the division defect of cdc28 mutants with defects at Start. Slt2p(Mpk1p) is a member of the MAP kinase family (Lee, K. S., K. Irie, Y. Gotoh, Y. Watanabe, H. Araki, E. Nishida, K. Matsumoto, and D. E. Levin. 1993. Mol. Cell. Biol. 13:3067-3075). We show that slt2 mutants exhibit phenotypes similar to those shown by mutants of the yeast actin cytoskeleton, including delocalization of chitin deposition and of actin cortical spots and the accumulation of secretory pathway membranes and vesicles. Furthermore, slt2::HIS3 act1-1 and slt2::HIS3 myo2-66 double mutants are inviable. We suggest that Slt2p functions downstream or in parallel with Cdc28p in promoting bud formation and apical growth.
Mazzoni
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Service de Biochimie et Génétique Moléculaire, Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
Zarov
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P
Rambourg
A
A
Mann
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C
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D017489:CDC28 Protein Kinase, S cerevisiae / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003599:Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D005800:Genes, Fungal; D005804:Genes, Lethal; D005838:Genotype; D008854:Microscopy, Electron; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010641:Phenotype; D011494:Protein Kinases / Q000235:genetics*; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D000199:Actins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017489:CDC28 Protein Kinase, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; C072724:SLT2 protein, S cerevisiae