Translational down-regulation of gene expression

Abstract

A mitochondrial tRNALys gene mutation at nucleotide position 8344 is responsible for the myoclonus epilepsy associated with ragged-red fibers (MERRF) subgroup of mitochondrial encephalomyopathies. Here, we show that normally modified uridine at the anticodon wobble position remains unmodified in the purified mutant tRNALys. We have reported a similar modification defect at the same position in two mutant mitochondrial tRNAsLeu(UUR) in another subgroup, mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), indicating this defect is common in the two kinds of tRNA molecules with the respective mutations of the two major mitochondrial encephalomyopathies. We therefore suggest the defect in the anticodon is responsible, through the translational process, for the pathogenesis of mitochondrial diseases.