RNA processing and degradation mechanisms shaping the mitochondrial transcriptome of budding yeasts

Abstract

Yeast mitochondrial genes are expressed as polycistronic transcription units that contain RNAs from different classes and show great evolutionary variability. The promoters are simple, and transcriptional control is rudimentary. Posttranscriptional mechanisms involving RNA maturation, stability, and degradation are thus the main force shaping the transcriptome and determining the expression levels of individual genes. Primary transcripts are fragmented by tRNA excision by RNase P and tRNase Z, additional processing events occur at the dodecamer site at the 3′ end of protein‐coding sequences. groups I and II introns are excised in a self‐splicing reaction that is supported by protein splicing factors encoded by the nuclear genes, or by the introns themselves. The 3′‐to‐5′ exoribonucleolytic complex called mtEXO is the main RNA degradation activity involved in RNA turnover and processing, supported by an auxiliary 5′‐to‐3′ exoribonuclease Pet127p. tRNAs and, to a lesser extent, rRNAs undergo several different base modifications. This complex gene expression system relies on the coordinated action of mitochondrial and nuclear genes and undergoes rapid evolution, contributing to speciation events. Moving beyond the classical model yeast Saccharomyces cerevisiae to other budding yeasts should provide important insights into the coevolution of both genomes that constitute the eukaryotic genetic system.

Editorial: The significance of mitogenomics in mycology, volume II

“…The removal of introns is facilitated by IEPs and various nuclear encoded protein factors (Mukhopadhyay and Hausner, 2021 ; Prince et al, 2022 ). Mitochondrial ribogenesis, processing of mitogenome derived transcripts, RNA degradation/turnover, and mRNA translation require many nuclear encoded factors (De Silva et al, 2017 ; Golik, 2023 ). The reliance on nuclear elements for mitochondrial gene expression links organellar function with nuclear cues in response to environmental and developmental factors.…”