An impaired RNA polymerase II activity in Saccharomyces cerevisiae causes cell-cycle inhibition at START.
Saccharomyces cerevisiae cells harboring the temperature-sensitive mutation rpo21-4, in the gene encoding the largest subunit of RNA polymerase II, were shown to be partially impaired for cell-cycle progress at a permissive temperature, and to become permanently blocked at the cell-cycle regulatory step, START, at a restrictive temperature. The rpo21-4 mutation was lethal in combination with cdc28 mutations in the p34 protein kinase gene required for START. Transcripts of the CLN1 and CLN2 genes, encoding G1-cyclin proteins that, along with p34, are necessary for START, were decreased in abundance by the rpo21-4 mutation at a restrictive temperature. Increased G1-cyclin production, by expression of the CLN1 or CLN2 genes from a heterologous GAL promoter, overcame the rpo21-4-mediated START inhibition, but such mutant cells nevertheless remained unable to proliferate at a restrictive temperature. These findings reveal that START can be particularly sensitive to an impaired RNA polymerase II function, presumably through effects on G1-cyclin expression.
Drebot
M A
MA
Department of Genetics, Hospital for Sick Children, Toronto, Ontario, Canada.
Johnston
G C
GC
Friesen
J D
JD
Singer
R A
RA
D002453:Cell Cycle; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D012319:RNA Polymerase II / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology*; D013696:Temperature; D014158:Transcription, Genetic
D016213:Cyclins; D012319:RNA Polymerase II