Identification of a novel TATA element-binding protein binding region at the N terminus of the Saccharomyces cerevisiae TAF1 protein

TFIID, a multiprotein complex composed of TATA element-binding protein (TBP) and 14 TBP-associated factors (TAFs), can directly recognize core promoter elements and mediate transcriptional activation. The TAF N-terminal domain (TAND) of TAF1 may play a significant role in these two principal TFIID functions by regulating the access of TBP to the TATA element. In yeast, TAND consists of two subdomains, TAND1 (10-37 amino acids (aa)) and TAND2 (46-71 aa), which interact with the concave and convex surfaces of TBP, respectively. Here we demonstrate that another region located on the C-terminal side of TAND2 (82-139 aa) can also bind to TBP and induce transcriptional activation when tethered to DNA as a GAL4 fusion protein. As these properties are the same as those of TAND1, we denoted this sequence as TAND3. Detailed mutational analyses revealed that three blocks of hydrophobic amino acid residues located within TAND3 are required not only for TBP binding and transcriptional activation but also for supporting cell growth and the efficient transcription of a subset of genes. We also show that the surface of TBP recognized by TAND3 is broader than that recognized by TAND1, although these regions overlap partially. Supporting these observations is that TAND1 can be at least partly functionally substituted by TAND3.