Serizawa H, Conaway J W, Conaway R C
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104.
Nature. 1993 May 27;363(6427):371-4. doi: 10.1038/363371a0.
Phosphorylation of the heptapeptide repeats in the C-terminal domain (CTD) of the largest subunit of RNA polymerase II has been widely proposed as an essential step in transcription initiation on the basis of findings indicating (1) that the CTDs of RNA polymerase II molecules actively engaged in transcription are highly phosphorylated; (2) that polymerase molecules containing non-phosphorylated CTDs preferentially enter the preinitiation complex where they are subsequently phosphorylated; and (3) that essential initiation factors b from yeast, delta from rat, and BTF2(TFIIH) from human cells have closely associated CTD-kinase activities. Here we take advantage of a highly purified enzyme system which supports both CTD phosphorylation and basal transcription to test this hypothesis directly. Using the isoquinoline sulphonamide derivative H-8, which is a potent inhibitor of CTD kinase, we show that basal transcription occurs in the absence of CTD phosphorylation.
基于以下研究结果，RNA聚合酶II最大亚基的C端结构域（CTD）中七肽重复序列的磷酸化被广泛认为是转录起始的关键步骤：（1）活跃参与转录的RNA聚合酶II分子的CTD高度磷酸化；（2）含有未磷酸化CTD的聚合酶分子优先进入起始前复合物，随后在其中被磷酸化；（3）酵母中的基本起始因子b、大鼠中的δ因子以及人类细胞中的BTF2（TFIIH）具有紧密相关的CTD激酶活性。在此，我们利用一种高度纯化的酶系统，该系统既支持CTD磷酸化又支持基础转录，以直接检验这一假设。使用异喹啉磺酰胺衍生物H - 8，它是CTD激酶的有效抑制剂，我们发现基础转录在没有CTD磷酸化的情况下也会发生。
