Chromatin-remodeling SWI/SNF complex regulates coenzyme Q₆ synthesis and a metabolic shift to respiration in yeast

Despite its relatively streamlined genome, there are many important examples of regulated RNA splicing in Saccharomyces cerevisiae Here, we report a role for the chromatin remodeler SWI/SNF in respiration, partially via the regulation of splicing. We find that a nutrient-dependent decrease in Snf2 leads to an increase in splicing of the PTC7 transcript. The spliced PTC7 transcript encodes a mitochondrial phosphatase regulator of biosynthesis of coenzyme Q₆ (ubiquinone or CoQ₆) and a mitochondrial redox-active lipid essential for electron and proton transport in respiration. Increased splicing of PTC7 increases CoQ₆ levels. The increase in PTC7 splicing occurs at least in part due to down-regulation of ribosomal protein gene expression, leading to the redistribution of spliceosomes from this abundant class of intron-containing RNAs to otherwise poorly spliced transcripts. In contrast, a protein encoded by the nonspliced isoform of PTC7 represses CoQ₆ biosynthesis. Taken together, these findings uncover a link between Snf2 expression and the splicing of PTC7 and establish a previously unknown role for the SWI/SNF complex in the transition of yeast cells from fermentative to respiratory modes of metabolism.