Taggart A K, Fisher T S, Pugh B F
Department of Molecular and Cell Biology, Pennsylvania State University, University Park 16802.
Cell. 1992 Dec 11;71(6):1015-28. doi: 10.1016/0092-8674(92)90396-t.
RNA polymerases I, II, and III require the TATA-binding protein (TBP) to initiate promoter-specific transcription. We have separated HeLa TBP into four phosphocellulose fractions that elicit polymerase specificity in supplying TBP activity to TBP-depleted pol II and pol III transcription reactions. Polymerase specificity might arise in part through distinct TBP-associated factors (TAFs), which have recently been identified in pol I and II transcription. However, the requirement for pol III TAFs has not been established. Here we show that classical pol III transcription involves a minimum of two novel TAFs: TAF-172 and TAF-L. Not only does TAF-172 activate pol III transcription, but it also inhibits the binding of TBP to the TATA box, thereby repressing pol II transcription. The TBP-TAF-172-TAF-L complex can replace TFIIIB both in transcription reactions reconstituted with TFIIIC and in template commitment assays. Thus SL1, TFIID, and TFIIIB might be functionally similar TBP-TAF complexes that direct pol I, II, and III transcription, respectively.
RNA聚合酶I、II和III需要TATA结合蛋白（TBP）来启动启动子特异性转录。我们已将HeLa TBP分离成四个磷酸纤维素级分，这些级分在向TBP缺失的pol II和pol III转录反应提供TBP活性时引发聚合酶特异性。聚合酶特异性可能部分源于不同的TBP相关因子（TAFs），这些因子最近已在pol I和II转录中被鉴定出来。然而，对pol III TAFs的需求尚未确定。在这里，我们表明经典的pol III转录至少涉及两种新的TAFs：TAF - 172和TAF - L。TAF - 172不仅激活pol III转录，还抑制TBP与TATA框的结合，从而抑制pol II转录。TBP - TAF - 172 - TAF - L复合物在由TFIIIC重构的转录反应和模板结合测定中都可以替代TFIIIB。因此，SL1、TFIID和TFIIIB可能是功能相似的TBP - TAF复合物，分别指导pol I、II和III转录。
