Fig. S6.

PC is associated with Ser5-P Pol II in Sg4 cells. Immunoblots of Pol II (Ser5-P form), PSC, and BRM from IPs by anti-PC and anti-BRM in Sg4 cells without (lanes 1–4) or with (lanes 5–7) overnight treatment with 50 μM RNA synthesis inhibitor 5,6-dichlorobenzimidazole 1-β-D-ribofuranoside (DRB) from Sigma. Lanes 1 and 5 are 5% inputs of cell extracts. Rabbit preimmune serum was used in lane 2 for a negative control. Note that PSC remained coimmunoprecipitated with PC in DRB-treated Sg4 cells but Ser5-P Pol II co-IP with PC was impaired in DRB treated cells (compare lane 6 with lane 3).