Phatnani Hemali P, Greenleaf Arno L
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Genes Dev. 2006 Nov 1;20(21):2922-36. doi: 10.1101/gad.1477006.
The C-terminal repeat domain (CTD), an unusual extension appended to the C terminus of the largest subunit of RNA polymerase II, serves as a flexible binding scaffold for numerous nuclear factors; which factors bind is determined by the phosphorylation patterns on the CTD repeats. Changes in phosphorylation patterns, as polymerase transcribes a gene, are thought to orchestrate the association of different sets of factors with the transcriptase and strongly influence functional organization of the nucleus. In this review we appraise what is known, and what is not known, about patterns of phosphorylation on the CTD of RNA polymerases II at the beginning, the middle, and the end of genes; the proposal that doubly phosphorylated repeats are present on elongating polymerase is explored. We discuss briefly proteins known to associate with the phosphorylated CTD at the beginning and ends of genes; we explore in more detail proteins that are recruited to the body of genes, the diversity of their functions, and the potential consequences of tethering these functions to elongating RNA polymerase II. We also discuss accumulating structural information on phosphoCTD-binding proteins and how it illustrates the variety of binding domains and interaction modes, emphasizing the structural flexibility of the CTD. We end with a number of open questions that highlight the extent of what remains to be learned about the phosphorylation and functions of the CTD.
C末端重复结构域（CTD）是附加在RNA聚合酶II最大亚基C末端的一个特殊延伸结构域，它作为众多核因子的灵活结合支架；与哪些因子结合取决于CTD重复序列上的磷酸化模式。随着聚合酶转录基因，磷酸化模式的变化被认为能协调不同因子与转录酶的结合，并强烈影响细胞核的功能组织。在这篇综述中，我们评估了关于RNA聚合酶II的CTD在基因起始、中间和末端的磷酸化模式已知和未知的情况；探讨了延伸中的聚合酶上存在双磷酸化重复序列这一观点。我们简要讨论了已知在基因起始和末端与磷酸化CTD结合的蛋白质；更详细地探讨了被招募到基因主体的蛋白质、它们功能的多样性以及将这些功能与延伸中的RNA聚合酶II拴系在一起的潜在后果。我们还讨论了关于磷酸化CTD结合蛋白不断积累的结构信息，以及它如何阐明结合结构域和相互作用模式的多样性，强调了CTD的结构灵活性。我们最后提出了一些开放性问题，突出了关于CTD的磷酸化和功能仍有待了解的程度。
