Expression of the Mitochondrial Genes in Saccharpmyces cerevisiae: Analysis of Translation and Transcription Products in Repressed and Derepressed Cells

Abstract

Several observations have shown that in Saccharomyces cerevisiae the expression of mitochondrial genes is subject to regulatory mechanisms resulting from the action of nuclear and mitochondrial genes. However, much is still unknown about the main regulated event, i.e., respiratory induction (Slonimski 1953; Perlman and Mahler 1974); this event takes place after a shift from anaerobiosis to aerobiosis, or during release from glucose repression, and it involves a strong increase in the expression of mitochondrial genes. All known mitochondrial translation products are actually present in anaerobic or glucose-repressed cells (Woodrow and Schatz 1979; Agostinelli et al. 1980a), but in different proportions as compared with respiring cells. The observed manyfold increase in mitochondrial protein synthesis is paralleled by an increase in the availability of cytoplasmically made factors such as RNA polymerase (Levens et al. 1980) and of subunits of respiratory enzymes encoded in the nucleus, but a direct cause-and-effect relationship has not been established. Differences in the compositions of mitochondrial tRNA populations in repressed and derepressed cells have also been observed (Baldacci et al. 1979). The hyperrepressibility of some box mutants (Pajot et al. 1977; Alexander et al. 1979) increases the complexity of this picture.

We report here an analysis of the mitochondrial translation and transcription products in repressed and derepressed cells and during respiratory induction. The strains used were D273-10B, PS409, ID41-6/161, and the isonuclear strain ID41-6/161 mD273 (kindly supplied by P. Perlman, Ohio State University, Columbus, Ohio) containing mitochondria from strain D273-10B.

RESULTS AND DISCUSSION
Growing repressed and derepressed cells...