Decreasing mitochondrial RNA polymerase activity reverses biased inheritance of hypersuppressive mtDNA

Daniel Corbi,Angelika Amon,David M Macalpine

doi:10.1371/journal.pgen.1009808

Daniel Corbi, Angelika Amon + Show 1 more

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https://doi.org/10.1371/journal.pgen.1009808

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Abstract

Faithful inheritance of mitochondrial DNA (mtDNA) is crucial for cellular respiration/oxidative phosphorylation and mitochondrial membrane potential. However, how mtDNA is transmitted to progeny is not fully understood. We utilized hypersuppressive mtDNA, a class of respiratory deficient Saccharomyces cerevisiae mtDNA that is preferentially inherited over wild-type mtDNA (rho+), to uncover the factors governing mtDNA inheritance. We found that some regions of rho+ mtDNA persisted while others were lost after a specific hypersuppressive takeover indicating that hypersuppressive preferential inheritance may partially be due to active destruction of rho+ mtDNA. From a multicopy suppression screen, we found that overexpression of putative mitochondrial RNA exonuclease PET127 reduced biased inheritance of a subset of hypersuppressive genomes. This suppression required PET127 binding to the mitochondrial RNA polymerase RPO41 but not PET127 exonuclease activity. A temperature-sensitive allele of RPO41 improved rho+ mtDNA inheritance over a specific hypersuppressive mtDNA at semi-permissive temperatures revealing a previously unknown role for rho+ transcription in promoting hypersuppressive mtDNA inheritance.

Highlights

The mitochondrion is an essential eukaryotic organelle and the site for many critical metabolic reactions such as iron-sulfur cluster metabolism, heme biosynthesis, the TCA cycle, and cellular respiration/oxidative phosphorylation [1,2,3]
From a multicopy suppression screen, we found that overexpression of putative mitochondrial RNA exonuclease PET127 reduced biased inheritance of a subset of hypersuppressive genomes
Functional mitochondrial DNA is important for cells to maintain fitness and too much damaged mitochondrial DNA can cause debilitating diseases in humans

Summary

Introduction

The mitochondrion is an essential eukaryotic organelle and the site for many critical metabolic reactions such as iron-sulfur cluster metabolism, heme biosynthesis, the TCA cycle, and cellular respiration/oxidative phosphorylation [1,2,3]. Most mitochondrial proteins are encoded by the nuclear DNA, made in the cytosol and imported into mitochondria [4,5]. Mitochondria have their own genome (mtDNA) containing a small number of genes that encode core components of complexes involved in cellular respiration/oxidative phosphorylation and machinery to translate those genes [6,7]. Loss of respiratory function caused either by partial disruption of mtDNA (rho-) or total loss of the mtDNA (rho0) results in impaired cellular respiration/oxidative phosphorylation and a slower colony growth phenotype. This reduced growth occurs even in non-respiratory conditions and is called petiteness [11,12]. MtDNA must be faithfully replicated, maintained, and segregated to progeny to maintain cellular fitness, mtDNA inheritance is not fully understood [13,14,15,16,17]

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