Determinants of vaccinia virus early gene transcription termination.
Determinants of vaccinia virus early gene transcription termination.
复制标题
痘苗病毒早期基因转录终止的决定因素。
DOI：
10.1016/j.virol.2008.03.011
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发表时间：
2008
期刊：
影响因子：
3.7
通讯作者：
Niles,EdwardG
中科院分区：
文献类型：
--
作者：
Piacente,Sarah;Christen,Linda;Dickerman,Benjamin;Mohamed,MohamedR;Niles,EdwardG
牛痘病毒早期基因转录需要牛痘终止因子、VTF、核苷三磷酸磷酸水解酶I、NPH I、ATP、病毒体RNA聚合酶和在新生RNA中的基序UUUUUNU，在体内，在距多聚腺苷酸添加位点30至50个碱基内发现。在这项研究中，牛痘早期基因转录终止效率，终止基序特异性和延伸率之间的关系进行了研究。低转录延伸率使终止效率最大化，并使UUUUUNU基序的特异性最小化。将终止基序定位在RNA聚合酶上游的63个碱基区域上允许有效的转录本释放，表明转录终止复合物具有显著的可塑性。在进行中的转录过程中观察到有效的转录本释放，独立于VTF或UUUUUNU，但需要NPH I和ATP或dATP。这说明了一个两步模型：指定步骤，需要VTF和UUUUUNU，和能量依赖的步骤，采用NPH I和ATP。对NPH I突变体刺激转录延伸能力的评估表明，需要ATP酶活性和NPH I与病毒RNA聚合酶的Rap94亚基之间的稳定相互作用。这些观察结果表明，NPH I是延伸RNA聚合酶的组分，其在转录延伸期间具有催化活性。
Vaccinia virus early gene transcription requires the vaccinia termination factor, VTF, nucleoside triphosphate phosphohydrolase I, NPH I, ATP, the virion RNA polymerase, and the motif, UUUUUNU, in the nascent RNA, found within 30 to 50 bases from the poly A addition site, in vivo. In this study, the relationships among the vaccinia early gene transcription termination efficiency, termination motif specificity, and the elongation rate were investigated. A low transcription elongation rate maximizes termination efficiency and minimizes specificity for the UUUUUNU motif. Positioning the termination motif over a 63 base area upstream from the RNA polymerase allowed efficient transcript release, demonstrating a remarkable plasticity in the transcription termination complex. Efficient transcript release was observed during ongoing transcription, independent of VTF or UUUUUNU, but requiring both NPH I and either ATP or dATP. This argues for a two step model: the specifying step, requiring both VTF and UUUUUNU, and the energy-dependent step employing NPH I and ATP. Evaluation of NPH I mutants for the ability to stimulate transcription elongation demonstrated that ATPase activity and a stable interaction between NPH I and the Rap94 subunit of the viral RNA polymerase are required. These observations demonstrate that NPH I is a component of the elongating RNA polymerase, which is catalytically active during transcription elongation.