FIG. 1.

In vitro CTD phosphorylation by various kinases allows binding of Ceg1. Glutathione-agarose carrying GST-CTD was phosphorylated with [γ-³²P]ATP by various kinases. Lanes: 1, no kinase; 2, Kin28-Ccl1; 3, Srb10-Srb11; 4, CTDK1; 5, casein kinase 1. Phosphorylated GST-CTD [GST-CTD(P)] and nonphosphorylated GST-CTD glutathione-agarose beads were incubated with Ceg1 and Cet1. The beads were pelleted and washed extensively. Phosphorylation of GST-CTD was detected by autoradiogram [GST-CTD(*P)] and immunoblotting [α-CTD(P)] with the H14 monoclonal antibody. GST-CTD and GST-CTD(P) were detected by immunoblotting with anti-GST antibody. Capping enzyme in the pellet was detected by both on autoradiogram of enzyme-GMP formation (Ceg1-*pG) and immunoblotting (α-Ceg1) with anti-Ceg1 antibody.