Fig. 6. mRNA levels are decreased in the wat1 mutant. (A) Northern analysis of tbp1⁺ transcripts with specific probes for intron and exon sequences. Wild-type (lanes 1 to 3), ts prp2 mutants (lanes 4 to 6) or wat1-deleted cells (lanes 7 to 9) were shifted from 26°C to 36°C, and total RNAs were prepared at 0 (lanes 1, 4 and 7), 2 hours (lanes 2, 5 and 8) and 4 hours (lanes 3, 6 and 9). 20 µg RNA was run in each lane. Northern hybridisation was performed using probes specific for intron (upper) or exon sequence (lower) corresponding to the tbp1⁺ gene. (B) Steady state transcript levels of various genes. RNA samples from wild-type (lanes 1 and 2) or wat1-deleted cells (lanes 3 to 5) prepared in A were used to examine transcript levels of nda2⁺, cdc2⁺, cig2⁺ and act1⁺. Equal loading (20 µg) of RNA was confirmed with ethidium bromide staining of the gel (not shown).