Regulation of Mitochondrial Gene Expression in Saccharomyces cerevisiae

This chapter focuses on the regulation of mitochondrial gene expression in yeast (Saccharomyces cerevisiae), and tries to explain how these gene expression is regulated. The chapter comprises the newer information on nuclearly encoded factors that affect mitochondrial transcription; mRNA processing, stability, and translation; and posttranslational modification and assembly. Transcription of yeast mitochondrial operons appears to be somewhat more complicated than transcription of phage genes but less complex than E. coli transcription. The 9-bp mitochondrial promoter is positioned immediately upstream of the start of transcription, which is reminiscent of the spacing of the polymerase recognition sequence in T3 and T7 phage genes. Though the mitochondrial enzyme contains two subunits, the catalytic subunit RP041 has considerable sequence similarity to the single subunit T-odd polymerases. With the exception of one transcript, that for a second tRNAthr, mitochondrial transcription units are multigenic. In some cases the initial transcripts contain multiple tRNAs, in other cases combinations of mRNAs and tRNAs or rRNAs and tRNAs. The RNAs involved in mitochondrial translation are all encoded on the mitochondrial genome, including the large and small ribosomal RNAs and the tRNAs.