FIG. 3.

Parafibromin (Parafib) interacts with the RNA polymerase large subunit. (A) 293T cell lysates were immunoprecipitated (IP) with antiparafibromin antibody Ab648, a peptide-blocked control (C), or a normal rabbit serum control and immunoblotted with antibodies to Rpb1 with unphosphorylated (Unphos.) CTD (top part), Ser5-phosphorylated CTD (second part), Ser2-phosphorylated CTD (third part), and parafibromin (bottom part). (B) 293T cell lysate was fractioned on a glycerol gradient. Forty-microliter aliquots of the fractions depicted were used for immunoblotting with anti-Rpb1 Ser5-phosphorylated CTD (top part), anti-hLeo1 antibody Ab677 (second part), antiparafibromin antibody Ab648 (third part), anti-hCtr9 antibody Ab679 (fourth part), anti-hPaf1 antibody Ab673 (fifth part), and anti-hRtf1 antibody (bottom part).