Nuclear Gene MTO1Regulates Aminoglycoside Sensitivity Of Yeast Carrying Mitochondrial15S RRNA C1409G Mutation And Mechanism Research

Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy. Mitochondria are encoded by nuclear genes and mitochondrial genes, so nuclear genes and mitochondrial gene mutations will affect the mitochondrial function.Mitochondria have been implicated in many human diseases, which are named mitochondrial disorders.The yeast MT01gene encodes an evolutionarily conserved protein for the biosynthesis of the5-carbo-xymethylaminomethyl group of cmnm5s2U in the wobble position of mitochondrial tRNA. The human mitochondrial12S rRNA A1555G mutation has been found to be associated with aminoglycoside-induced and non-syndromic deafness.Yeast15S rRNA C1409G is homologous mutation of A1555G. This article use yeast as model organism, and study yeast strains series of different nuclear gene mutation and/or mitochondrial mutations, through the methods of phenotype identification and mechanism analysis. This model will enable us to put nuclear modifier gene, mitochondrial mutations and antibiotics as a whole system to study.Gene mtol null mutant expressed the respiratory deficient phenotype only when coupled with the C1409G mutation of mitochondrial15S rRNA.When under antibiotics environment, the yeast whose mitochondrial genes are wild type can grow with a certain degree of inhibition, but they are still grow well with little phenotype difference. This shows the nuclear modifier gene MTO1knockout or not does not affect the yeast cells’normal growth in aminoglycoside antibiotics, and the strains are resistant to antibiotics. The strain of wild nuclear gene and mitochondrial mutations is almost impossible to survive, the phenotype undergone an obvious change, so the strain is very sensitive to antibiotics. And the strain of both nuclear and mitochondrial mutations grows better, the strain’s sensitivity to antibiotic reduces and the antibiotic resistance increase. The nuclear modifier gene indeed plays a role in regulating the expression of mitochondrial mutations.The mechanism study is about the reason of the phenotype. The analysis about the mitochondrial RNA level, membrane potential and oxygen consumption show that mitochondrial function of the strain of both nuclear and mitochondrial mutations is weaker than the strain of wild nuclear gene and mitochondrial mutation. There has been no recovery of mitochondrial function, after the use of aminoglycoside. In the study of glycolytic pathway, the expression of the glycolytic key enzyme of the double mutation strain is higher than the strain of wild nuclear gene and mitochondrial mutation, both in the RNA level and protein level. So the nuclear gene MTO1may be associated with the glycolytic pathway and increase energy production to compensate for respiratory defects, resulting in this phenotype.The experiments of aminoglycoside antibiotics resistance show no visible difference in these strains, so it is not the reason.4,5-substituted aminoglycoside antibiotics show the same phenotype with neomycin. Yeast15S rRNA1477-1583(1409-1491) base pair is important to the sensitivity of yeast strains to neomycin. In the analysis of strains of MTOl、MT02、 MSS1, the protein level of hexokinase in the glycolytic pathway show differences. The analysis of genes interacting with MTO1suggests that MTO1knockout may influence cAMP to activate glycolytic pathway.This finding study the role of nuclear modifier gene in aminoglycoside toxicity related to mitochondrial mutations. This will help to understand the mechanism of phenotypic diversity of mitochondrial diseases, which are controlled by the nuclear genes, mitochondrial genes, and environmental factors...