RNA Processing in Yeast Mitochondria

Abstract

The yeast mitochondrial genome is remarkably complex in terms of the organization of its genes and their modes of expression. The first indications of this came a number of years ago with the construction of detailed transcription maps of mtDNA in related yeast strains (Van Ommen and Groot 1977; Van Ommen et al. 1979), and we predicted at that time (Grivell et al. 1979) that RNA processing would play a central role in the regulation of mitochondrial gene expression. With the insights gained from DNA sequence analysis and transcript characterization, it is clear that this prediction has been amply fulfilled. In this paper we review what is known about a number of yeast mtRNAs and the various forms of processing they undergo in the hope that this will lead to a better understanding of the mechanisms that control the expression of this genome.

TRANSCRIPTION INITIATION AND TRIMMING OF mtRNAS
15S and 21S rRNAs
In human mtDNA, transcription is initiated at a single site on each strand and the genome is completely and symmetrically transcribed (Murphy et al. 1975). Differential control of gene expression is then achieved by a combination of transcription attenuation, control of the cleavages required to generate transcripts of individual genes, and the stability of the final products (see Attardi et al., this volume). In yeast, a greater scope of transcriptional controls exists, since Levens et al. (1980) have identified at least five possible promoter sites by means of the guanylyl transferase capping assay (Reeder et al. 1977)...