Recruitment of Human TBP Selectively Activates RNA Polymerase II TATA-dependent Promoters
Journal of Biological Chemistry
An increasing body of evidence suggests that eukaryotic activators stimulate polymerase II transcription by facilitating the assembly of the functional basal machinery at the promoter. Here we describe experiments that provide added support for the idea that recruitment of TATA-binding protein (TBP) is a rate-limiting step for transcription activation in mammalian cells. We found that, in human cell lines, recruitment of TBP to a promoter, as a GAL4-TBP fusion protein, can provide a substantial
... activation of transcription. Activation mediated by the hTBP, tethered to promoter DNA, is strictly dependent upon the presence of a functional TATA element, and it directs faithful transcription initiation. Interestingly, GAL4-hTBP activation was not observed from initiator (Inr) -dependent TATA-less promoters. These results suggest that TBP binding to DNA is not a rate-limiting step for the initial stages of TFIID recruitment to initiator-dependent TATA-less promoters. Finally, we provide evidence that synergy between GAL4-hTBP and defined transcription domains is restricted to activators, such as VP16 and Tat, which are likely to function at steps subsequent to the TFIID recruitment.