In this report, we investigated the molecular genetic mechanism underlying the
deafness-associated mitochondrial
tRNAHis 12201T>C mutation. The destabilization of a highly conserved base-pairing (5A-68U) by the m.12201T>C mutation alters structure and function of
tRNAHis. Using cybrids constructed by transferring mitochondria from lymphoblastoid cell lines derived from a Chinese family into
mtDNA-less (ρo) cells, we showed ∼70% decrease in the steady-state level of
tRNAHis in mutant cybrids, compared with control cybrids. The mutation changed the conformation of
tRNAHis, as suggested by slower electrophoretic mobility of mutated
tRNA with respect to the wild-type molecule. However, ∼60% increase in aminoacylated level of
tRNAHis was observed in mutant cells. The failure in
tRNAHis 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
tRNAHis mutation leading to
deafness.