A deafness-associated tRNAHis mutation alters the mitochondrial function,ROS production and membrane potential

In this report, we investigated the molecular genetic mechanism underlying the deafness-associated mitochondrial tRNA^His 12201T>C mutation. The destabilization of a highly conserved base-pairing (5A-68U) by the m.12201T>C mutation alters structure and function of tRNA^His. Using cybrids constructed by transferring mitochondria from lymphoblastoid cell lines derived from a Chinese family into mtDNA-less (ρ^o) cells, we showed ∼70% decrease in the steady-state level of tRNA^His in mutant cybrids, compared with control cybrids. The mutation changed the conformation of tRNA^His, as suggested by slower electrophoretic mobility of mutated tRNA with respect to the wild-type molecule. However, ∼60% increase in aminoacylated level of tRNA^His was observed in mutant cells. The failure in tRNA^His metabolism was responsible for the variable reductions in seven mtDNA-encoded polypeptides in mutant cells, ranging from 37 to 81%, with the average of ∼46% reduction, as compared with those of control cells. The impaired mitochondrial translation caused defects in respiratory capacity in mutant cells. Furthermore, marked decreases in the levels of mitochondrial ATP and membrane potential were observed in mutant cells. These mitochondrial dysfunctions caused an increase in the production of reactive oxygen species in the mutant cells. The data provide the evidence for a mitochondrial tRNA^His mutation leading to deafness.