FIG. 8.

Involvement of Sip1 in spliceosome assembly. The splicing complexes were formed with ³²P-labeled pPIP85.A pre-mRNA at different time points in the presence of ATP, using nuclear extracts which were immunodepleted (depl.) by using the preimmune or anti-Sip1 serum (lanes 1 to 4 and 5 to 8, respectively). The splicing complexes were separated on a native 4% polyacrylamide gel by electrophoresis. The autoradiograph of the gel is shown. Positions of A and B complexes and nonspecific H complex are indicated.