Interactions between SL snRNP proteins. (A) SL75p interacts with SL21p and SL26p independent of RNA. Western blot of proteins immunoprecipitated from embryonic extract. Some samples were treated with RNase (+) before IP. The blot was probed with anti-SL26p or anti-SL21p, as indicated on the left. IP antibodies are shown at the top. In each case, input and IP samples shown on the gels are approximately equal percentages of the total. (B) Destruction of snRNAs by RNase 1. Northern blot of RNAs isolated from extract used in panel A. RNAs were detected by hybridization with 32P-labeled oligonucleotides complementary to SL2 RNA, SL1 RNA, and Sm Y. The Sm Y probe recognizes a number of the Sm Y family members and appears on the Northern blot as a doublet. (Lane 1) control; (lane 2) RNase-treated. (C) SL26p is part of an Sm snRNP. Western blot probed with anti-SL26p antibody. RNase treated (+). IP: lanes 3 and 4, Kung patient serum (anti-Sm); lanes 5 and 6, nonimmune rabbit serum.
