Jeong S W, Lang W H, Reeder R H
Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
J Biol Chem. 1996 Jul 5;271(27):16104-10. doi: 10.1074/jbc.271.27.16104.
A transcription terminator for RNA polymerase I (polI) in the yeast, Saccharomyces cerevisiae, is composed of two essential elements, the 11bp binding site for Reb1p and an upstream T-rich element coding for the last 10-12 nucleotides of the terminated transcript. We now show that, if the upstream element is changed to homopolymer T residues, polI undergoes iterative slippage, long poly(U) tails are added to the transcript, and termination is impaired. Reinsertion of one or two non-T residues within a critical region prevents iterative slippage and reinstates termination. A survey of naturally occurring terminators reveals that many contain T-rich upstream regions with non-T residues situated appropriately to prevent slippage. We discuss the possibility that the first step in slippage, backward sliding of both the transcript and the catalytic center of the polymerase, may be an obligatory step in the normal termination process.
酿酒酵母中RNA聚合酶I（polI）的转录终止子由两个必需元件组成，即Reb1p的11bp结合位点和一个富含T的上游元件，该元件编码终止转录本的最后10 - 12个核苷酸。我们现在表明，如果将上游元件改变为同聚物T残基，polI会发生迭代滑动，转录本会添加长聚（U）尾，并且终止会受到损害。在关键区域重新插入一两个非T残基可防止迭代滑动并恢复终止。对天然存在的终止子的调查表明，许多终止子含有富含T的上游区域，其中非T残基的位置适当以防止滑动。我们讨论了滑动的第一步，即转录本和聚合酶催化中心的向后滑动，可能是正常终止过程中一个必不可少的步骤的可能性。
