Pausing and termination by bacteriophage T7 RNA polymerase
Pausing and termination by bacteriophage T7 RNA polymerase
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DOI：
10.1006/jmbi.1998.1854
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发表时间：
1998-07-10
影响因子：
5.6
通讯作者：
McAllister, WT
中科院分区：
文献类型：
--
作者：
Lyakhov, DL;He, B;McAllister, WT
已知有两种类型的位点可引起噬菌体T7 RNA聚合酶(RNAP)的暂停和/或终止。在第I类位点的终止(由在T7DNA的晚期区域T Phi中发现的信号代表)涉及在终止点之前在新生RNA中形成稳定的茎环结构，并导致在U第II类位点附近的终止，由首先在克隆的人甲状旁腺激素原(PTH)基因中鉴定的信号来代表，在RNA中不产生明显的结构，但在终止点之前包含保守序列，并且还包含U在第I类和第II类位点的终止可能涉及不等价的机制，作为T7RNA聚合酶的突变体，已被鉴定为不能识别II类位点，但仍能识别I类位点的突变。在这项工作中，我们分析了几个二类站点的暂停和终止及其变体。我们的结论是，7bp的ATCTGTT序列(非模板链中的5‘到3’)导致转录T7或T3RNA聚合酶暂停。在该序列之后的6到8个碱基对Il的存在有利，这可能是因为它们破坏了RNA：DNA杂交的稳定性。T7溶菌酶对暂停和终止的影响与终止涉及聚合酶从伸长构象回到起始构象的想法是一致的，并且溶菌酶抑制到伸长构象的返回。提出了一个暂停和终止的动力学模型，该模型对我们的结果提供了一致的解释。(C)1998年学术出版社。
Two types of sites are known to cause pausing and/or termination by bacteriophage T7 RNA polymerase (RNAP). Termination at class I sites (typified by the signal found in the late region of T7 DNA, T Phi) involves the formation of a stable stem-loop structure in the nascent RNA ahead of the point of termination, and results in termination near runs of U. Class II sites, typified by a signal first identified in the cloned human preproparathyroid hormone (PTH) gene, generate no evident structure in the RNA but contain a conserved sequence ahead of the point of termination, and also contain runs of U. Termination at class I and class II sites may involve non-equivalent mechanisms, as mutants of T7 RNA polymerase have been identified that fail to recognize class II sites yet continue to recognize class I sites. In this work, we have analyzed pausing and termination at several class II sites, and variants of them. We conclude that the 7 bp sequence ATCTGTT (5' to 3' in the non-template strand) causes transcribing T7 or T3 RNA polymerase to pause. Termination 6 to 8 bp past this sequence is favored by the presence of runs of Il, perhaps because they destabilize an RNA:DNA hybrid. The effects of T7 lysozyme on pausing and termination are consistent with the idea that termination involves a reversion of the polymerase from the elongation to the initiation conformation, and that lysozyme inhibits the return to the elongation conformation. A kinetic model of pausing and termination is presented that provides a consistent interpretation of our results. (C) 1998 Academic Press.