Chodosh L A, Fire A, Samuels M, Sharp P A
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
J Biol Chem. 1989 Feb 5;264(4):2250-7.
The purine nucleoside analog 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) is a selective inhibitor of transcription by RNA polymerase II. Although a wealth of in vivo studies have suggested that DRB inhibits transcription by enhancing the premature termination of elongating polymerase molecules, in vitro studies to date have been interpreted to suggest that DRB acts at the level of transcription initiation. We have analyzed the mechanism of DRB-mediated transcription inhibition in vitro both in HeLa whole cell extracts and in a partially purified transcription system. The results indicate that the extent to which DRB inhibits the synthesis of a RNA transcript is directly proportional to its length. For example, DRB was found to preferentially inhibit transcription in vitro of promoter-distal relative to promoter-proximal portions of the adenovirus major late transcription unit. A factor potentially involved in mediating this inhibitory effect is identified. We conclude that the mechanism of DRB inhibition of transcription in vivo and in vitro are similar.
嘌呤核苷类似物5,6-二氯-1-β-D-呋喃核糖基苯并咪唑（DRB）是RNA聚合酶II转录的选择性抑制剂。尽管大量的体内研究表明DRB通过增强延伸的聚合酶分子的过早终止来抑制转录，但迄今为止的体外研究被解释为表明DRB在转录起始水平起作用。我们已经在HeLa全细胞提取物和部分纯化的转录系统中分析了DRB介导的体外转录抑制机制。结果表明，DRB抑制RNA转录本合成的程度与其长度成正比。例如，发现DRB在体外优先抑制腺病毒主要晚期转录单位启动子远端相对于启动子近端部分的转录。鉴定出一种可能参与介导这种抑制作用的因子。我们得出结论，DRB在体内和体外抑制转录的机制是相似的。
