Figure 6.

Fractionation of U4, U5 and U6 RNPs on sucrose gradients. (A) Extracts were prepared and separated on sucrose gradients as in Fig. 1. The sucrose gradient fractions were subjected to Northern blot analysis with antisense U5 RNA probe. (B) Tagging the U4, U5, and U6 snRNPs using antisense oligonucleotides. RNPs from the sucrose gradient fractions were incubated with end-labeled oligonucleotides to U4 (oligonucleotide 6), U5 (oligonucleotide 3), and U6 (oligonucleotide 4) and the RNPs were separated on native gels. The fractions are numbered from top to bottom. S values were determined relative to rRNA 28S, 18S, and 4S (GIBCO/BRL) and catalase (11S). The particles were designated as following: I, monomeric particles, except from the ≈18S U5 particle (I*); II, U4/U6 dimeric particle; and III, the tri–snRNP complex U4/U6⋅U5.