Functional Domains and Upstream Activation Properties of Cloned Human TATA Binding Protein

The TATA binding protein, TFIID, plays a central role in the initiation of eukaryotic mRNA synthesis. Here, we present a human cDNA clone for this factor. Comparison of its predicted protein sequence with those from Drosophila and yeast reveals a highly conserved carboxylterminal 180 amino acids. By contrast, the amino-terminal region of TFIID has diverged in both sequence and length. A striking feature of the human protein is a stretch of 38 glutamine residues in the NH$_2$-terminal region. Expression of human TFIID in both Escherichia coli and HeLa cells produces a protein that binds specifically to a TATA box and promotes basal transcription; the conserved GOOH-terminal portion of the protein is snfficient for both of these activities. Recombinant TFIID forms a stable complex on a TATA box either alone or in combination with either of the general transcription factors, TFIIA or TFIIB. Full-length recombinant TFIID is able to support Spl activated transcription in a TFIIDdepleted nuclear extract, while a deletion of the NH$_2$-terminal half of the protein is not. These results indicate the importance of the NH$_2$-terminal region for upstream activation functions and suggest that additional factors (co-activators) are required for mediating interactions with specific regulators.