CLONING AND CHARACTERIZATION OF AN ESSENTIAL SACCHAROMYCES-CEREVISIAEGENE, TAF40, WHICH ENCODES YTAF(II)40, AN RNA-POLYMERASE II-SPECIFIC TATA-BINDING PROTEIN-ASSOCIATED FACTOR

In this report we describe the cloning and initial characterization of TAF40, a gene that encodes a yeast TATA-binding protein-associated fa ctor (yTAF) of M(r) = similar to 40,000. This gene has many similariti es to other yTAFs described thus far in that it is present at a single copy per haploid genome, it is essential for viability, and the deduc ed protein sequence of yTAF40 exhibits similarity to previously descri bed human and Drosophila TAF(II)s. Immunological studies confirm that yTAF40 protein is a subunit of a large multiprotein TATA binding prote in-TAF complex that contains a subset of the total number of the yTAFs present in yeast cell extracts. Transcription reactions performed usi ng yeast whole cell extracts reveal that of the three nuclear RNA poly merases only RNA polymerase II function is abrogated when yTAF40 and a ssociated proteins are immunodepleted from solution, indicating that t he functionality of the multiprotein complex containing yTAF40 is RNA polymerase II-specific. By these criteria yTAF40 appears to encode a b ona fide RNA polymerase II-specific TAF, and thus the protein that it encodes has been termed yTAF(II)40.