Drebot M A, Johnston G C, Friesen J D, Singer R A
Department of Genetics, Hospital for Sick Children, Toronto, Ontario, Canada.
Mol Gen Genet. 1993 Nov;241(3-4):327-34. doi: 10.1007/BF00284685.
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.
携带温度敏感突变rpo21 - 4的酿酒酵母细胞，该突变位于编码RNA聚合酶II最大亚基的基因中，研究表明，在允许温度下，这些细胞的细胞周期进程会部分受损，而在限制温度下，它们会在细胞周期调控步骤START处永久受阻。rpo21 - 4突变与START所需的p34蛋白激酶基因中的cdc28突变结合时是致死的。CLN1和CLN2基因的转录本，它们编码G1 - 细胞周期蛋白，与p34一起是START所必需的，在限制温度下，rpo21 - 4突变会使其丰度降低。通过从异源GAL启动子表达CLN1或CLN2基因来增加G1 - 细胞周期蛋白的产生，克服了rpo21 - 4介导的START抑制，但这些突变细胞在限制温度下仍然无法增殖。这些发现表明，START可能对受损的RNA聚合酶II功能特别敏感，大概是通过对G1 - 细胞周期蛋白表达的影响。
