TRANSCRIPTION TERMINATION AT INTRINSIC TERMINATORS - THE ROLE OF THE RNA HAIRPIN
TRANSCRIPTION TERMINATION AT INTRINSIC TERMINATORS - THE ROLE OF THE RNA HAIRPIN
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DOI：
10.1073/pnas.92.19.8793
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发表时间：
1995-09-12
影响因子：
11.1
通讯作者：
VONHIPPEL, PH
中科院分区：
文献类型：
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作者：
WILSON, KS;VONHIPPEL, PH
大肠杆菌中转录的内在终止涉及新生RNA中RNA发夹的形成，该发夹在DNA模板上的内在终止位点处的转录物和聚合酶的释放中起核心作用。我们已经创建了λ tR 2终止子发夹的变体，并检查了该发夹的结构和稳定性与模板位置和终止效率之间的关系，结果用于测试Yager和von Hippel的简单核酸去稳定化模型，并表明必须修改该模型以提供新生RNA中富含rU的序列的独特作用，因为足够长以形成可以使整个推定的12-bp RNA DNA杂交体去稳定化的RNA发夹的完美回文序列不会在预期位置处触发终止，相反，我们的结果表明，有效的内在终止需要稳定的终止子发夹和紧接着的6-8个rU残基，并且终止发生在相对于这两种组分的特异性和不变的模板位置。根据这些发现和最近的结果，提出了简单模型的可能的结构或动力学修改，这些结果涉及“尺蠖”和内在终止中转录复合物的可能构象异质性，因此，这些发现表明发夹的结构和尺寸是终止的重要决定因素，延伸决定，并建议一个完整的机制可能涉及聚合酶，RNA终止子发夹，也许，富含dT的模板序列，其编码新生转录物3'末端的rU残基的运行。
Intrinsic termination of transcription in Escherichia coli involves the formation of an RNA hairpin in the nascent RNA, This hairpin plays a central role in the release of the transcript and polymerase at intrinsic termination sites on the DNA template, We have created variants of the lambda tR2 terminator hairpin and examined the relationship between the structure and stability of this hairpin and the template positions and efficiencies of termination, The results were used to test the simple nucleic acid destabilization model of Yager and von Hippel and showed that this model must be modified to provide a distinct role for the rU-rich sequence in the nascent RNA, since a perfect palindromic sequence that is sufficiently long to form an RNA hairpin that could destabilize the entire putative 12-bp RNA DNA hybrid does not trigger termination at the expected positions, Rather, our results show that both a stable terminator hairpin and the run of 6-8 rU residues that immediately follows are required for effective intrinsic termination and that termination occurs at specific and invariant template positions relative to these two components. Possible structural or kinetic modifications of the simple model are proposed in the light of these findings and of recent results implicating ''inchworming'' and possible conformational heterogeneity of transcription complexes in intrinsic termination, Thus, these findings argue that the structure and dimensions of the hairpin are important determinants of the termination-elongation decision and suggest that a complete mechanism is likely to involve specific interactions of the polymerase, the RNA terminator hairpin, and, perhaps, the dT-rich template sequence that codes for the run of rU residues at the 3' end of the nascent transcript.