Fig. 1.

An Sm-precipitable factor is necessary for efficient Drosophila pre-mRNA processing. (A) Total RNA from decreasing amounts of a Drosophila nuclear extract (lanes 1–3) and the RNA species precipitated by anti-Sm Ab (lane 4) were resolved in a denaturing polyacrylamide gel and detected by silver staining. The arrow indicates the position of a putative Drosophila U7 snRNA. (B) In vitro processing of Drosophila-specific dH3* pre-mRNA in a Kc nuclear extract preincubated with a nonspecific mAb (mock, lane 1) or with anti-Sm Ab (αSm, lane 2).