FIG. 2.

The Taf1p-region 4 polypeptide alone nucleates assembly of a partial TFIID complex in vivo. (A) Schematic representation of Taf1p (top) and region 4 (amino acid residues 200 to 303; bottom). The gray and the hatched boxes represent the NLS (PKKKRKV) and HA₃ tag, respectively, of the expression vector fused to region 4 coding sequence and expressed from a GAL enhancer-promoter on a 2μm plasmid. (B) Co-IP analysis of TAF proteins associated with Taf1p-region 4. WCEs were prepared from yeast cells expressing empty vector containing the NLS and HA₃ tag only (Empty Vector) or vector-NLS-HA₃-region 4 sequence (Vector Region4) and precleared with protein A beads. Immunoprecipitates were formed from these precleared WCEs by using anti-HA immunoglobulin G bound to protein A beads. The resulting immunoprecipitates were fractionated by SDS-PAGE, blotted, and probed with specific antibodies as indicated (left). Input (I) lanes represent 1% of the total WCE used for each IP; pellet (P) lanes represent the total immunoprecipitated material.