J. Biol. Chem., Vol. 265, Issue 13, 7449-7454, May, 1990
Discoordinate expression of the yeast mitochondrial ribosomal protein MRP1
H Dang, G Franklin, K Darlak, AF Spatola and SR Ellis
Department of Biochemistry, University of Louisville, Kentucky 40292.
We have examined expression of the protein coded within the MRP 1 locus of
Saccharomyces cerevisiae. Direct evidence is provided for the assignment of
the MRP1 gene product as a protein component of the small subunit of
mitochondrial ribosomes. Further studies examined the extent to which the
expression of the MRP1 protein is coordinated with the expression of other
mitochondrial ribosomal components coded in the nuclear and mitochondrial
genomes. Extra copies of the MRP1 gene were introduced into yeast cells to
perturb expression from MRP1 relative to other mitochondrial ribosomal
components to determine whether forms of regulation function to limit the
accumulation of either MRP1 mRNA or protein under these conditions.
Increases in MRP1 gene dosage were accompanied by substantial increases in
both MRP1 mRNA and protein, indicating that their accumulation was not
linked to the level of expression of other mitochondrial ribosomal
components. This conclusion was confirmed by additional studies that showed
that the accumulation of the MRP1 protein was unaffected in cells that did
not express mitochondrially-encoded rRNAs. These results contrast with
previous studies on the expression of two other mitochondrial ribosomal
proteins indicating that regulatory properties of mitochondrial ribosomal
proteins are quite diverse.