Gusarov I, Nudler E
Department of Biochemistry, New York University Medical Center, New York 10016, USA.
Mol Cell. 1999 Apr;3(4):495-504. doi: 10.1016/s1097-2765(00)80477-3.
In bacteria, an intrinsic transcription termination signal appears in RNA as a hairpin followed by approximately eight uridines (U stretch) at the 3' terminus. This signal leads to rapid dissociation of the ternary elongation complex (TEC) into RNA, DNA, and an RNA polymerase. We demonstrate that the hairpin inactivates and then destabilizes TEC by weakening interactions in the RNA-DNA hybrid-binding site and the RNA-binding site that hold TEC together. Formation of the hairpin is restricted to the moment when TEC reaches the point of termination and depends upon melting of four to five hybrid base pairs that follow the hairpin's stem. The U stretch-induced pausing at the point of termination is crucial, providing additional time for hairpin formation. These results explain the mechanism of termination and aid in understanding of how cellular factors modulate this process.
在细菌中，一种内在转录终止信号在RNA中表现为一个发夹结构，随后在3'末端有大约八个尿苷（U序列）。该信号导致三元延伸复合物（TEC）迅速解离为RNA、DNA和RNA聚合酶。我们证明，发夹结构通过削弱使TEC保持在一起的RNA-DNA杂交结合位点和RNA结合位点中的相互作用，使TEC失活并随后使其不稳定。发夹结构的形成仅限于TEC到达终止点的时刻，并取决于发夹茎之后四到五个杂交碱基对的解链。U序列在终止点诱导的暂停至关重要，为发夹结构的形成提供了额外的时间。这些结果解释了终止机制，并有助于理解细胞因子如何调节这一过程。
