Figure 7. ZASC1 binds to active and inactive forms of P-TEFb.

HEK293 cells (1×10⁸) were transfected with expression plasmids encoding Myc-tagged ZASC1 and eGFP. 48 h post-transfection, cells were treated with 10 µM DRB or 1 µg/ml actinomycin D for one h, lysed, fractionated on a 5% to 45% glycerol gradient and (A) analyzed by western blot with the indicated antibodies. (B) The indicated gradient fractions were pooled and immunoprecipitated with either a non-specific mouse IgG or mouse anti-Myc IgG. Input (I) non-specific (N) and myc-ZASC1 (Z) immunoprecipitations were analyzed by western blot with the indicated antibodies. All blots are representative of at least three independent experiments.