25 Genetics of Mitochondrial Translation

Abstract

CELLULAR ORGANIZATION
Cellular genetic systems of eukaryotic microorganisms, and most tissues of multicellular organisms, must produce thousands of different proteins with widely different fates. This contrasts sharply with the role of mitochondrial genetic systems, which carry out the specialized and limited task of supplying only a few proteins that are subunits of energy-transducing complexes imbedded in the inner membrane. Although this unequal division of labor has been observed in all eukaryotic species examined, considerable species to species variation exists in the spectrum of proteins coded in mitochondrial DNA (mtDNA), the arrangement of their genes in mtDNA, the structure of their messenger RNAs, and even the genetic code used to specify their amino acid sequences. This chapter cannot attempt to cover mitochondrial gene expression broadly (for this, see Attardi and Schatz 1988; Gray 1989; Costanzo and Fox 1990; Hanson and Folkerts 1992; Dieckmann and Staples 1994). Instead, the focus will be on the budding yeast Saccharomyces cerevisiae as a model system in which it has been possible to bring genetic tools to bear on the study of mitochondrial translation in vivo, making occasional comparative comments on other species.

With the exception of a single mitochondrially coded ribosomal protein, all of the known proteins comprising the yeast mitochondrial translation system are coded by nuclear genes, synthesized in the cytoplasm, and imported into the organelles (see Fig. 1) (for review, see Costanzo and Fox 1990; Dieckmann and Staples 1994; Pel and Grivell 1994). Thus, more than 100 nuclear genes are required to allow...