Interactions between hRPB11a, hRPB11bα and hRPB11bβ proteins with the twelve GST-hRPB subunits. Sf9 cells were coinfected with two recombinant baculoviruses, the first expressing one of the twelve GST-fused subunits or GST alone, the second expressing the untagged hRPB11a, bα or bβ subunits. After metabolic labelling of proteins using 35S Met, extracts were prepared and GST-pulldown assays were performed. Aliquots of the total extracts (Extracts) and of the GST-bound fractions (GST-pulldown) were analysed by SDS-PAGE and revealed by autoradiography. Arrows point to the position of the non-tagged hRPB11a, bα or bβ subunits.