Steady state analysis of mitochondrial RNA after growth of yeast Saccharomyces cerevisiae under catabolite repression and derepression.

The steady state levels of mitochondrial rRNAs, 5 tRNAs, the 9 S RNA, and the RNA products from the genes coding for subunits 6 and 9 of the ATP synthase, cytochrome b, and subunit 1 of cytochrome oxidase have been determined after growth of yeast under conditions of respiratory repression or derepression. The analysis indicates that the mitochondrial rRNAs are present in 2000 or 9000 copies/cell in repressed or derepressed yeast, respectively. The levels of the other RNAs also differed to a similar extent, with the exception of the level of the tRNAfMet which differs by only 1.7-fold. The levels of the individual protein coding RNAs varied from 480 copies/cell for the Oli-1 RNA to 100 copies/cell for the Oli-2 RNA under derepressive conditions and from 130 copies/cell to 33 copies/cell for the same RNAs in glucose repressive conditions. The levels of the tRNAs varied even more markedly, ranging from 4200 copies/cell for the tRNAPhe to 240 copies/cell for the tRNACys after growth in derepressive conditions and from 800 copies/cell for the tRNAfMet to 30 copies/cell for the tRNACys of glucose repressed yeast. These results indicate that glucose repression uniformly decreases the levels of the individual mitochondrial RNAs studied. This decrease is related to a lower synthesis of mitochondrial RNA in the glucose repressed cells as compared to derepressed cells.