Komissarova Natalia, Becker Jodi, Solter Stephanie, Kireeva Maria, Kashlev Mikhail
NCI Center for Cancer Research, Frederick Cancer Research and Development Center, Frederick, MD 21702, USA.
Mol Cell. 2002 Nov;10(5):1151-62. doi: 10.1016/s1097-2765(02)00738-4.
Passage of E. coli RNA polymerase through an intrinsic transcription terminator, which encodes an RNA hairpin followed by a stretch of uridine residues, results in quick dissociation of the elongation complex. We show that folding of the hairpin disrupts the three upstream base pairs of the 8 bp RNA:DNA hybrid, a major stability determinant in the complex. Shortening the weak rU:dA hybrid from 8 nt to 5 nt causes dissociation of the complex. During termination, the hairpin does not directly compete for base pairing with the 8 bp hybrid. Thus, melting of the hybrid seems to result from spatial restrictions in RNA polymerase that couple the hairpin formation with the disruption of the hybrid immediately downstream from the stem. Our results suggest that a similar mechanism disrupts elongation complexes of yeast RNA polymerase II in vitro.
大肠杆菌RNA聚合酶通过一个内在转录终止子（其编码一个RNA发夹结构，后面跟着一段尿苷残基），会导致延伸复合物迅速解离。我们发现，发夹结构的折叠会破坏8 bp RNA:DNA杂交体的三个上游碱基对，而这是该复合物中一个主要的稳定性决定因素。将弱的rU:dA杂交体从8个核苷酸缩短到5个核苷酸会导致复合物解离。在终止过程中，发夹结构并不直接与8 bp杂交体竞争碱基配对。因此，杂交体的解链似乎是由RNA聚合酶中的空间限制导致的，这种空间限制将发夹结构的形成与茎下游紧邻的杂交体的破坏联系起来。我们的结果表明，类似的机制在体外会破坏酵母RNA聚合酶II的延伸复合物。
