FIG. 6.

Direct interaction of Taf1p-region 4 with Taf4p and Taf6p. (A) Yeast two-hybrid interactions between DBD-Taf1p-region 4 bait and Taf4p- and Taf6p-AD fusion proteins. Yeast strains harboring either no bait (−) or a Taf1p-region 4 (Reg4)-containing DBD bait (amino acids 235 to 395) and either empty AD vector (−), AD-Taf4p, or AD-Taf6p were plated on appropriate selection medium containing 3 mM 3-aminotriazole. Equal numbers of cells for each strain were serially threefold diluted and spotted on plates (dilutions top to bottom). Cells expressing full-length Gal4p served as a positive control. (B) Taf4p and Taf6p interact directly with (GST-)region 4. E. coli carrying either Taf4p or Taf6p expression plasmids was induced with IPTG as detailed in Materials and Methods, and bacterial cell extracts were prepared. Equal amounts of precleared E. coli cell lysates were incubated with equal amounts of GST or region 4-GST fusion proteins (bottom) bound to glutathione-agarose beads. Pellets containing GST-bound proteins were fractionated by SDS-PAGE, blotted, and probed for Taf6p (top) or Taf4p (middle) binding by using antibodies to either Taf6p or Taf4p (left).