FIG. 1.

Assay for U4/U6 assembly. (A) Total cell RNA was extracted from a wild-type yeast strain (lanes 1 and 2) or a strain in which the U4 snRNA gene was replaced by U4* (lanes 3 and 4). After RNA extraction at 4°C, RNA was incubated for 10 min at either 20°C (lanes 1 and 3) or 70°C (lanes 2 and 4) prior to being loaded on a native polyacrylamide gel. After transfer to nylon membranes, identical filters were hybridized with an oligonucleotide probe specific for the wild-type U4 snRNA (left panel) or the U4* snRNA (right panel). (B) Total cell RNA was extracted from strain BSY295 grown for 0, 0.5, 1, 2, and 4 h in the presence of galactose. After native gel electrophoresis and transfer to a nylon membrane, the expression of the U4* snRNA was detected with a radioactively labelled oligonucleotide complementary to U4*. A labelled U1-specific oligonucleotide probe was included, as U1 snRNA served as a loading control.