Fig. 6. The ini1⁺ gene is required for pre-mRNA splicing. (A-F) RT-PCR analysis of cwf8⁺, cdc2⁺ and tfIId⁺, ade2+, nda3⁺ and rpl7⁺ RNAs isolated from the temperature sensitive prp2 mutant cells at the permissive (25°C) or the restrictive (36°C) temperature, and from Rep81ini1⁺ cells grown in the absence (–Th) or presence (+Th) of thiamine for 12 hours. Unspliced and processed mRNAs are indicated. DNA molecular mass markers (M) are also shown. (G) Northern blot analysis of pre-mRNA and mRNA for the gene encoding U6 snRNA isolated from prp2-1 cells at 25°C and 36°C and from ini1 cells with or without thiamine for 12 hours. See Materials and Methods for details. Lower panel shows ethidium bromide-stained gel of 5S RNA, as a loading control.