Scafe C, Chao D, Lopes J, Hirsch J P, Henry S, Young R A
Whitehead Institute for Biomedical Research, Nine Cambridge Center, Massachusetts 02142.
Nature. 1990 Oct 4;347(6292):491-4. doi: 10.1038/347491a0.
The large subunit of RNA polymerase II contains a highly conserved and essential heptapeptide repeat (Pro-Thr-Ser-Pro-Ser-Tyr-Ser) at its carboxy terminus. Saccharomyces cerevisiae cells are inviable if their RNA polymerase II large subunit genes encode fewer than 10 complete heptapeptide repeats; if they encode 10 to 12 complete repeats cells are temperature-sensitive and cold-sensitive, but 13 or more complete repeats will allow wild-type growth at all temperatures. Cells containing C-terminal domains (CTDs) of 10 to 12 complete repeats are also inositol auxotrophs. The phenotypes associated with these CTD mutations are not a consequence of an instability of the large subunit; rather, they seem to reflect a functional deficiency of the mutant enzyme. We show here that partial deletion mutations in RNA polymerase II CTD affect the ability of the enzyme to respond to signals from upstream activating sequences in a subset of promoters in yeast. The number of heptapeptide repeats required for maximal response to signals from these sequences differs from one upstream activating sequence to another. One of the upstream elements that is sensitive to truncations of the CTD is the 17-base-pair site bound by the GAL4 transactivating factor.
RNA聚合酶II的大亚基在其羧基末端含有一个高度保守且必不可少的七肽重复序列（脯氨酸-苏氨酸-丝氨酸-脯氨酸-丝氨酸-酪氨酸-丝氨酸）。如果酿酒酵母细胞的RNA聚合酶II大亚基基因编码的完整七肽重复序列少于10个，则这些细胞无法存活；如果编码10至12个完整重复序列，细胞对温度敏感且对寒冷敏感，但13个或更多完整重复序列将允许在所有温度下野生型生长。含有10至12个完整重复序列的C末端结构域（CTD）的细胞也是肌醇营养缺陷型。与这些CTD突变相关的表型并非大亚基不稳定的结果；相反，它们似乎反映了突变酶的功能缺陷。我们在此表明，RNA聚合酶II CTD中的部分缺失突变会影响该酶对酵母中一部分启动子上游激活序列发出的信号作出反应的能力。对这些序列的信号作出最大反应所需的七肽重复序列数量因一个上游激活序列而异。对CTD截短敏感的上游元件之一是由GAL4反式激活因子结合的17个碱基对位点。
