Fig. 7. p14 is present in both major and minor spliceosomes. (A) Anti-p14 antibodies precipitate U2-dependent spliceosomes. Splicing was performed for 5 (lanes 1–3) or 20 min (lanes 4–6) with MINX pre-mRNA and immunoprecipitations (IPs) carried out with pre-immune (NIS; lanes 2 and 5) or anti-p14 (lanes 3 and 6) serum. Twenty percent of the splicing reaction used for IP is also shown (lanes 1 and 4). (B) Anti-p14 antibodies precipitate U12-dependent spliceosomes. Splicing was performed for 30 (lanes 1–6) or 240 min (lanes 7–12) with P120 pre-mRNA in the presence of an oligonucleotide against U2 (lanes 1–3 and 7–9) or U12 (lanes 4–6 and 10–12). IPs were carried out with pre-immune (NIS; lanes 2, 5, 8 and 11) or anti-p14 (lanes 3, 6, 9 and 12) serum. Twenty percent of the splicing reaction used for IP is also shown (lanes 1, 4, 7 and 10). RNA was analyzed as described in Materials and methods and visualized by autoradiography.