ISOLATION AND CHARACTERIZATION OF TAF25, AN ESSENTIAL YEAST GENE THATENCODES AN RNA-POLYMERASE II-SPECIFIC TATA-BINDING PROTEIN-ASSOCIATEDFACTOR

We describe the cloning and analysis of TAF25, a previously uncharacte rized yeast gene that encodes a yeast TATA-binding protein-associated factor or yTAF or M(r) = 25,000. The gene encoding yTAF25 is a single copy essential gene, and the protein sequence deduced from TAF25 exhib its sequence similarity to a metazoan hTAF(II). The results for immuno logical studies confirm that yTAF25 is a subunit of a large multiprote in TATA-binding protein-yeast TATA-binding protein-associated factor c omplex that contains a subset of the total number of the yTAFs present in yeast cell extracts. Both genetic and biochemical analyses demonst rate that yTAF25 can interact directly with itself. Transcriptional da ta show that the activity of the multiprotein complex containing yTAF2 5 is RNA polymerase II-specific, thus indicating that TAF25 encodes a bona fide yeast RNA polymerase II TAF. Hence the protein encoded by TA F25 has been termed yTAF (II)25.