FIG. 3.
pX binds endogenous as well as C34,37S TFIIB mutants but not R290E mutant. (A) Distinct pX-transfected cell extracts (HA tagged or not, as indicated) were immunoprecipitated) (IP) with anti-HA (α-HA), and the resulting proteins were analyzed by SDS-PAGE and anti-TFIIB immunoblotting. (B) Nuclear extracts (5%) of pHA-TFIIB and pflag-X-transfected cells, as well as fractions that were immunoprecipitated with α-flag, were analyzed by anti-HA immunoblotting. (C) The level of coimmunoprecipitation of the wild-type TFIIB was compared to that of C34,37S mutant. (D) Recombinant GST-X, wt TFIIB, and TFIIB mutants were resolved by SDS-PAGE, blotted, and reacted with 32P-labeled recombinant pX. Shown is the resulting autoradiogram.