Yeast homologues of higher eukaryotic TFIID subunits.
In eukaryotic cells the TATA-binding protein (TBP) associates with other proteins known as TBP-associated factors (TAFs) to form multisubunit transcription factors important for gene expression by all three nuclear RNA polymerases. Computer searching of the complete Saccharomyces cerevisiae genome revealed five previously unidentified yeast genes with significant sequence similarity to known human and Drosophila RNA polymerase II TAFs. Each of these genes is essential for viability. A sixth essential gene (FUN81) has previously been noted to be similar to human TAFII18. Coimmunoprecipitation experiments show that all six proteins are associated with TBP, demonstrating that they are true TAFs. Furthermore, these proteins are present in complexes containing the TAFII130 subunit, indicating that they are components of TFIID. Based on their predicted molecular weights, these genes have been designated TAF67, TAF61(68), TAF40, TAF23(25), TAF19(FUN81), and TAF17. Yeast TAF61 is significantly larger than its higher eukaryotic homologues, and deletion analysis demonstrates that the evolutionarily conserved, histone-like domain is sufficient and necessary to support viability.