Mitochondrial mRNA and the small subunit rRNA in budding yeasts undergo 3'-end processing at conserved...

Area of Science:

• Mitochondrial biology
• Molecular genetics
• Eukaryotic gene expression

Background:

• Mitochondrial protein synthesis relies on organelle ribosomes and mRNAs.
• RNA maturation and stability are critical for mitochondrial gene expression but poorly understood.
• 3'-end processing factors for mitochondrial RNAs are largely unknown.

Purpose of the Study:

• To investigate the molecular mechanisms of mitochondrial mRNA 3'-end processing in Saccharomycotina yeasts.
• To identify and characterize cis- and trans-acting factors involved in this process.
• To explore the evolutionary conservation and functional implications of these mechanisms.

Main Methods:

• Mapping of 3' ends of mitochondrial mRNAs across diverse yeast species.
• Identification of species-specific sequence elements (3'-RPEs).
• Biochemical analysis of interactions between Rmd9 orthologs and 3'-RPEs.

Main Results:

• Discovered species-specific 3'-end RNA processing elements (3'-RPEs) in mitochondrial RNAs.
• Demonstrated that Rmd9 orthologs interact with their cognate 3'-RPEs in Debaryomycetaceae yeasts.
• Observed 3'-RPEs upstream of stop codons in specific mRNAs, with subsequent stop codon removal.

Conclusions:

• Rmd9-dependent processing of mitochondrial RNA precursors is a conserved mechanism in Saccharomycotina.
• The findings suggest Rmd9 is essential for mitochondrial mRNA metabolism and mitoribosome biogenesis.
• Stop codon removal in specific mRNAs implies noncanonical translation termination mechanisms in certain yeasts.