Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom.
J Biol Chem. 2010 Jul 2;285(27):20564-9. doi: 10.1074/jbc.M110.132530. Epub 2010 May 10.
The carboxyl-terminal domain (CTD) of the largest subunit of RNA polymerase II (pol II) comprises multiple tandem repeats of the heptapeptide Tyr(1)-Ser(2)-Pro(3)-Thr(4)-Ser(5)-Pro(6)-Ser(7). This unusual structure serves as a platform for the binding of factors required for expression of pol II-transcribed genes, including the small nuclear RNA (snRNA) gene-specific Integrator complex. The pol II CTD specifically mediates recruitment of Integrator to the promoter of snRNA genes to activate transcription and direct 3' end processing of the transcripts. Phosphorylation of the CTD and a serine in position 7 are necessary for Integrator recruitment. Here, we have further investigated the requirement of the serines in the CTD heptapeptide and their phosphorylation for Integrator binding. We show that both Ser(2) and Ser(7) of the CTD are required and that phosphorylation of these residues is necessary and sufficient for efficient binding. Using synthetic phosphopeptides, we have determined the pattern of the minimal Ser(2)/Ser(7) double phosphorylation mark required for Integrator to interact with the CTD. This novel double phosphorylation mark is a new addition to the functional repertoire of the CTD code and may be a specific signal for snRNA gene expression.
RNA 聚合酶 II （pol II）最大亚基的羧基末端结构域（CTD）包含多个七肽重复序列 Tyr（1）-Ser（2）-Pro（3）-Thr（4）-Ser（5）-Pro（6）-Ser（7）。这种不寻常的结构充当了结合因子的平台，这些因子是 pol II 转录基因表达所必需的，包括小核 RNA （snRNA）基因特异性整合体复合物。pol II CTD 特异性介导整合体募集到 snRNA 基因的启动子，以激活转录并指导转录本的 3'端加工。CTD 的磷酸化和位置 7 上的丝氨酸对于整合体的募集是必需的。在这里，我们进一步研究了 CTD 七肽中丝氨酸及其磷酸化对整合体结合的要求。我们表明，CTD 的 Ser（2）和 Ser（7）都需要，并且这些残基的磷酸化对于有效结合是必需和充分的。使用合成的磷酸肽，我们确定了整合体与 CTD 相互作用所需的最小 Ser（2）/Ser（7）双重磷酸化标记的模式。这种新的双重磷酸化标记是 CTD 密码子功能谱的新补充，可能是 snRNA 基因表达的特异性信号。
