An impaired RNA polymerase II activity in Saccharomyces cerevisiae causes cell-cycle inhibition at START
1993
Drebot, M.A. | Johnston, G.C. | Friesen, J.D. | Singer, R.A.
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.
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