Fig. 6. Splicing and pre-mRNA leakage analyses. (A) ts mutants msl5-2, -3 and -9. The reporters contained the RP51A intron in the wild-type form (WT-intron) or with a mutation in the 5′ splice site (mut5′SS), in the branchpoint (mutBP) or in both (mut5′SS + mutBP) interrupting the reading frame of the lacZ gene. Another set of reporters contained a synthetic intron, which was designed in a way that either the mRNA (mRNA in frame) or the pre-mRNA (pre-mRNA in frame) would code for β-galactosidase. Activity is expressed as the relative activity of a construct containing no intron in the lacZ gene. The insets show enlarged details of the plots where necessary (note the different scales). (B) cs mutant msl5-5. The analysis was performed as in (A), but cells were grown at 30°C, transferred for 30 min at 16°C before induction for 4 h at 16°C.