FIG. 4.

The sad1-1 mutant is defective in the assembly of newly synthesized U4* snRNA. The sad1-1 strain and the unrelated temperature-sensitive and splicing-defective prpx-1 strain were grown for 0.5, 1, 2, and 4 h at 37°C. Subsequently, galactose was added and growth was continued for a further 2 h at 37°C. Following RNA extraction, separation on a native acrylamide gel, and transfer, labelled oligonucleotide probes were used to detect the U4* snRNA and U1 snRNA, which serves as a loading control (A). The same filter (after removal of the U1 and U4* probes) was hybridized with an oligonucleotide specific for the U4 snRNA (B).