PKC1, a protein kinase C homologue of Saccharomyces cerevisiae, participates in microtubule function through the yeast EB1 homologue, BIM1.
BACKGROUND
RSC is a chromatin-remodelling complex of Saccharomyces cerevisiae and essential for growth. Its catalytic subunit is encoded by the NPS1/STH1 gene. At the present time, little is known regarding the cellular function of RSC.


RESULTS
To identify genes with functions related to NPS1, we screened high-copy suppressor genes for the temperature- and thiabendazole (TBZ)-sensitive mutant allele of NPS1, nps1-105. Amongst the suppressors we cloned PKC1/STT1 and BIM1 that encoded a homologue of mammalian protein kinase C and a conserved microtubule binding protein homologous to human EB1, respectively. Both the temperature sensitive mutation of PKC1, stt1, and the bim1 null mutation caused synthetic growth defects with nps1-105. A genetic analysis of the functional relationships between these genes revealed that PKC1 suppressed the defect of nps1-105 through the BIM1 function but not by the activation of the MPK1/MAPK pathway. The stt1 mutation alone showed TBZ sensitivity and delayed the G2-phase progression at semi-permissive temperatures. Both of these stt1 phenotypes were suppressed by the over-expression of BIM1. In addition, stt1 as well as nps1-105, mis-segregated a mini-chromosome at frequencies higher than the wild-type at a permissive temperature. The mis-segregation was enhanced in the nps1-105 stt1 double mutant.


CONCLUSIONS
These results suggest that Pkc1p plays a role which is relevant to microtubule functions and that this role is mediated by a hitherto unknown PKC signalling pathway and by Bim1p
Hosotani
T
T
Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima, Japan 739-8527.
Koyama
H
H
Uchino
M
M
Miyakawa
T
T
Tsuchiya
E
E
D015152:Blotting, Northern; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D020090:Chromosome Segregation; D017931:DNA Primers / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000502:physiology*; D018628:Gene Dosage; D008868:Microtubule Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011493:Protein Kinase C / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D013827:Thiabendazole / Q000494:pharmacology
C119683:BIM1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D017931:DNA Primers; D005656:Fungal Proteins; D008868:Microtubule Proteins; D029701:Saccharomyces cerevisiae Proteins; C097993:Pkc1 protein, Trichoderma reesei; D011493:Protein Kinase C; D013827:Thiabendazole