FIG. 7.

PRP4K specifically cosediments with the 20S U5-snRNP during glycerol gradient centrifugation. (A) Proteins from each fraction of the glycerol gradient were separated by SDS-10% PAGE and visualized by Coomassie blue staining (Protein). Fractions that cosediment with the 12S U1/U2 snRNP, 20S U5-snRNP, and the U4/U6.U5 snRNP were determined by the position of the corresponding snRNAs (data not shown) as indicated above the panels. The positions of PRP4K, PRP6, the U1-specific U1-70K protein, the U5 snRNP-specific 200K and 220K proteins, and the U4/U6 snRNP-specific 90K, 61K, and 60K proteins are arrowed. (B and C) Western blot analysis of fractions with antibodies to PRP4K (B) or PRP6 (C).