Efficient termination of nuclear lncRNA transcription promotes mitochondrial genome maintenance

https://elifesciences.org/articles/31989

Dorine Jeanne Mariëtte du Mee, Maxim Ivanov, Joseph Paul Parker, Stephen Buratowski, Sebastian Marquardt

• Most of the DNA of eukaryotes does not code for protein, yet many such regions of non-coding DNA are still transcribed into RNA (these are called lncRNA). Understanding the biological functions of these large expanses of non-coding DNA is an active area of current research.
• Here, the authors show that a particular non-coding RNA in budding yeast (CUT60) is required for the proper transcription of its neighbouring gene ATP16. Mutations in CUT60 could result in the fusion of the lncRNA with the RNA of ATP16, and consequently the ATP16 protein could not be produced.
• Interestingly, this had the consequence of yeast cells losing their mitochondrial DNA. ATP16 constitutes a subunit of ATP-synthase, which perhaps explains this striking phenotype.
• The authors speculate that loss of mtDNA triggered by controlled, transient, transcription termination efficiency of CUT60 could allow cells to detoxify themselves of deleterious mtDNA 

Thoughts
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The authors raise an interesting idea that yeast cells may be able to cleans their mtDNA through reducing CUT60 transcription termination efficiency. They suggest that cells may shed their mtDNA, and then gain healthy copies of molecules through mating. We know from animals that, during development, the mtDNA bottleneck serves to cleanse the developing embryo of deleterious mtDNA mutations. I wonder whether yeast cells could use this mechanism to a gentler extent (not completely losing their mtDNA, just reducing their mtDNA copy number) to bottleneck their mtDNA?