Role for the Ssu72 C-terminal domain phosphatase in RNA polymerase II transcription elongation
Role for the Ssu72 C-terminal domain phosphatase in RNA polymerase II transcription elongation
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DOI：
10.1128/mcb.01361-06
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发表时间：
2007-02-01
影响因子：
5.3
通讯作者：
Hampsey, Michael
中科院分区：
文献类型：
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作者：
Reyes-Reyes, Mariela;Hampsey, Michael
RNA聚合酶II（RNAP II）转录周期伴随着C-末端结构域（CTD）磷酸化状态的变化，CTD是存在于最大RNAP II亚基C末端的重复七肽序列（Y1 S2 P3 T4 S5 P6 S7）。在这个过程中涉及的酶之一是Ssu 72，CTD磷酸酶与特异性丝氨酸-5-P。在这里，我们报告的Ssu 72 -2编码的Ssu 72-R129 A蛋白在体外催化受损和Ssu 72 -2突变体积累的丝氨酸-5-P形式的RNAP II在体内。一个来自ssu 72 -2突变体的体外转录系统表现出受损的延伸效率。RPB 1和RPB 2（编码RNAP 11的两个最大亚基的基因）中的突变被鉴定为ssu 72 -2的抑制基因。rpb 1 -1001抑制子编码R1281 A替换，而rpb 2 -1001编码R983 G替换。这一信息使我们确定了先前定义的rpb 2 -4和rpb 2 -10等位基因，它们编码RNAP II的催化缓慢形式，作为ssu 72 -2的额外抑制因子。此外，缺失编码Spt 4-Spt 5早期延伸复合物的亚基的SPT 4也抑制ssu 72 -2，而sptS-242等位基因被rpb 2 -1001抑制。这些结果将Ssu 72定义为转录延伸因子。我们提出了一个模型，其中Ssu 72催化丝氨酸-5-P去磷酸化后，添加的7-甲基鸟苷帽前mRNA的方式，促进RNAP II过渡到转录周期的延长阶段。
The RNA polymerase II (RNAP II) transcription cycle is accompanied by changes in the phosphorylation status of the C-terminal domain (CTD), a reiterated heptapeptide sequence (Y1S2P3T4S5P6S7) present at the C terminus of the largest RNAP II subunit. One of the enzymes involved in this process is Ssu72, a CTD phosphatase with specificity for serine-5-P. Here we report that the ssu72-2-encoded Ssu72-R129A protein is catalytically impaired in vitro and that the ssu72-2 mutant accumulates the serine-5-P form of RNAP II in vivo. An in vitro transcription system derived from the ssu72-2 mutant exhibits impaired elongation efficiency. Mutations in RPB1 and RPB2, the genes encoding the two largest subunits of RNAP 11, were identified as suppressors of ssu72-2. The rpb1-1001 suppressor encodes an R1281A replacement, whereas rpb2-1001 encodes an R983G replacement. This information led us to identify the previously defined rpb2-4 and rpb2-10 alleles, which encode catalytically slow forms of RNAP II, as additional suppressors of ssu72-2. Furthermore, deletion of SPT4, which encodes a subunit of the Spt4-Spt5 early elongation complex, also suppresses ssu72-2, whereas the sptS-242 allele is suppressed by rpb2-1001. These results define Ssu72 as a transcription elongation factor. We propose a model in which Ssu72 catalyzes serine-5-P dephosphorylation subsequent to addition of the 7-methylguanosine cap on pre-mRNA in a manner that facilitates the RNAP II transition into the elongation stage of the transcription cycle.