A hypertension-associated mitochondrial DNA mutation introduces an m1G37 modification into tRNAMet, altering its structure and function

Abstract

Defective nucleotide modifications of mitochondrial tRNAs have been associated with several human diseases, but their pathophysiology remains poorly understood. In this report, we investigated the pathogenic molecular mechanism underlying a hypertension-associated 4435A→G mutation in mitochondrial tRNA The m.4435A→G mutation affected a highly conserved adenosine at position 37, 3' adjacent to the tRNA's anticodon, which is important for the fidelity of codon recognition and stabilization. We hypothesized that the m.4435A→G mutation introduced an mG37 modification of tRNA, altering its structure and function. Primer extension and methylation activity assays indeed confirmed that the m.4435A→G mutation created a tRNA methyltransferase 5 (TRMT5)-catalyzed mG37 modification of tRNA We found that this mutation altered the tRNA structure, indicated by an increased melting temperature and electrophoretic mobility of the mutated tRNA compared with the wildtype molecule. We demonstrated that cybrid cell lines carrying the m.4435A→G mutation exhibited significantly decreased efficiency in aminoacylation and steady-state levels of tRNA, as compared with those of control cybrids. The aberrant tRNA metabolism resulted in variable decreases in mitochondrial DNA (mtDNA)-encoded polypeptides in the mutant cybrids. Furthermore, we found that the m.4435A→G mutation caused respiratory deficiency, markedly diminished mitochondrial ATP levels and membrane potential, and increased the production of reactive oxygen species in mutant cybrids. These results demonstrated that an aberrant mG37 modification of mitochondrial tRNA affected the structure and function of its tRNA and consequently altered mitochondrial function. Our findings provide critical insights into the pathophysiology of maternally inherited hypertension, which is manifested by the deficient tRNA nucleotide modification.

Obesity associated with a novel mitochondrial tRNACys 5802A>G mutation in a Chinese family

“…This hypothesis was further confirmed by an MD simulation, revealing that the m.5802A>G mutation changed the stability and mobility of tRNA secondary structure. Moreover, the m.5802A>G mutation perturbed the tRNA Cys conformation, and correspond to the altered electrophoretic mobility of mutated tRNAs carrying the m.4435A>G, m.3253T>C and m.15927A>G mutations [22,26,27]. In this family, obesity started setting in at 9.3 years age.…”

The mitochondrial transfer RNAAsp A7551G mutation may contribute to the clinical expression of deafness associated with the A1555G mutation in a pedigree with hearing impairment

“…In fact, A37 in tRNAs is often chemically modified (by thiolation or methylation) (22), therefore, the A7551G mutation may contribute to maintenance of the level of tRNA Asp (23). Notably, the well-known A4435G mutation occurring at the same position in the tRNA Met gene was previously found to be a risk factor for hypertension (24) and Leber's hereditary optic neuropathy (LHON) (25). Thus, the A7551G mutation, which is similar to the A4435G mutation, may have also resulted in failure of tRNA metabolism.…”

Effects of Oxidative Stress on Protein Translation: Implications for Cardiovascular Diseases

“…Such mutations of mitochondrial tRNA genes are related to numerous cardiomyopathy-associated pathological conditions like mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes, myoclonic epilepsy with ragged red fibers, and maternally inherited diabetes and deafness [161]. Similarly, a mitochondrial mutation resulting in a m 1 G37 modification of tRNA Met is related to maternally inherited hypertension [162]. A genetic study of nine infants belonging to five different families and suffering from severe cardiomyopathy revealed mutations in the GatCAB aminoacyl-tRNA amidotransferase complex, which charges the mt-tRNA Gln via a transamidation reaction [163].…”