FIG. 6.

Sedimentation of the U1 snRNP is altered after Prp42HAp depletion. GAL1::PRP42HA extracts prepared before (A) and after (B) metabolic depletion of Prp42HAp were fractionated on a 10 to 30% linear glycerol gradient. The snRNAs present in alternate gradient fractions were assayed by Northern blotting with a hybridization cocktail which probed for each of the spliceosomal snRNAs. The U1 snRNP fractions most sensitive to Prp42HAp depletion are indicated by asterisks. The location of the free U6 snRNP, the U4-U6 snRNP, and the U4-U6.U5 tri-snRNP are indicated below the figure. In both panels, sample 23 comes from the bottom of the gradient tube and contains all of the spliceosomal snRNAs, presumably, from native spliceosomes or nonspecific aggregates. T, total, unfractionated RNA.