Study on the mechanism of transcriptional regulation by the general transcription factor TFIID (The Role of WD

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The general transcription factor TFIID, which consists of TATA-binding protein (TBP) and TBP-associated factors (TAF5), plays a central role in transcription initiation by RNA polymerase II in eukaryotes. This study was carried out to understand the mechanism of transcriptional regulation by TFIID, focusing on the WD repeat-containing TAFs, TAF72 and TAF73, of the fission yeast Schizosaccharomyces pombe.TAF72 was used as bait in a two-hybrid screen to identify its interacting proteins. The screen yielded hitone H4-like TAF with a calculated molecular mass of 50 kDa, which was named TAF50. Coimmunoprecipitation experiments demonstrated that TAF50, as well as TAF72, is a component of the S. pombe TFIID complex. Both TAFs were also present in the SAGA complex, a histone acetyltransferase complex distinct from TFIID.To identify additional TAFs in S. pombe, database searches were performed, revealing that the S. pombe genome contains a set of TAFs homologous to those identified in other organisms.In addition, temperature-sensitive mutants of TAF72 and TAF73 were isolated to elucidate the in vivo function of these TAFs.These results uncover a function of the WD-repeat region of TAF72, that is, mediating interaction between TAFs, and also provide information about the basal transcription machinery of S. pombe. Furthermore, the temperature-sensitive mutants of TAF72 and TAF73 isolated in this study would serve as materials for future work.