FIGURE 4.

The absence of Mne1 attenuates splicing of the aI5β intron of COX1. Northern blot analysis of COX1 introns in WT and mne1Δ cells. The blots were hybridized with ³²P-labeled probes complementary to COX1 exon 6, COX1 introns aI1, aI2, aI3, aI4, aI5α-γ, and 21S rRNA exon 1. The schematic (top) shows the molecular organization of the COX1 gene from the intron-containing W303 strain and the size (in bp) of each intron is given below its name. Group I introns are indicated by a black line and group II introns by a gray line. Sizes for COX1 mRNA splice variants containing either single or multiple introns aI3, aI4, and/or aI5β are shown below. In the Northern panels we have indicated the position of the large and small ribosomal rRNAs as LSU and SSU, respectively, on the left. The numbers to the right of each Northern panel indicate the approximate size of the indicated transcripts.