Baculovirus expression of human U6-p110 mutant derivatives. The expression of wild-type U6-p110, splice variant AF 387506, and mutant proteins ΔC, ΔC10, RRM 1-2, and ΔN was detected by Coomassie blue staining (left panel) and by Western blotting (right panel). Molecular mass markers (in kilodaltons) are given on the left.