Mutant tRNA Research Articles

Mitochondrial tRNA mutations may be infrequent in hepatocellular carcinoma patients.

Mitochondrial DNA mutations have been shown to play important roles in the pathogenesis of hepatocellular carcinoma (HCC). In particular, genes encoding mitochondrial tRNA (mt-tRNA) are hotspots for pathogenic mutations associated with HCC. Recently, an increasing number of studies have reported the involvement of such mutations in this disease. As a result, several mt-tRNA mutations associated with HCC have been described. Some of these are neutral polymorphisms and may not cause mitochondrial dysfunction. Moreover, the molecular mechanisms by which these pathogenic mutations result in HCC remain unclear. To address this problem, we evaluated five mt-tRNA variants (tRNA(Val) T1659C, tRNA(Ala) G5650A, tRNA(Arg) T10463C, tRNA(Glu) A14679G, and tRNA(Pro) C15975T) implicated in the clinical manifestation of HCC in humans. We performed evolutionary conservation analysis and used a bioinformatic tool to predict the secondary structure of the mt-tRNAs carrying these mutations. Using an established pathogenicity scoring system, we classified T10463C and A14679G as neutral polymorphisms, and determined that the T1659C, G5650A, and C15975T variants should be regarded as pathogenic mutations. To the best of our knowledge, this is the first report to establish the pathogenicity of HCC-associated mt-tRNA mutations.

Rationally evolving tRNAPylfor efficient incorporation of noncanonical amino acids

Genetic encoding of noncanonical amino acids (ncAAs) into proteins is a powerful approach to study protein functions. Pyrrolysyl-tRNA synthetase (PylRS), a polyspecific aminoacyl-tRNA synthetase in wide use, has facilitated incorporation of a large number of different ncAAs into proteins to date. To make this process more efficient, we rationally evolved tRNAPyl to create tRNAPyl-opt with six nucleotide changes. This improved tRNA was tested as substrate for wild-type PylRS as well as three characterized PylRS variants (Nϵ-acetyllysyl-tRNA synthetase [AcKRS], 3-iodo-phenylalanyl-tRNA synthetase [IFRS], a broad specific PylRS variant [PylRS-AA]) to incorporate ncAAs at UAG codons in super-folder green fluorescence protein (sfGFP). tRNAPyl-opt facilitated a 5-fold increase in AcK incorporation into two positions of sfGFP simultaneously. In addition, AcK incorporation into two target proteins (Escherichia coli malate dehydrogenase and human histone H3) caused homogenous acetylation at multiple lysine residues in high yield. Using tRNAPyl-opt with PylRS and various PylRS variants facilitated efficient incorporation of six other ncAAs into sfGFP. Kinetic analyses revealed that the mutations in tRNAPyl-opt had no significant effect on the catalytic efficiency and substrate binding of PylRS enzymes. Thus tRNAPyl-opt should be an excellent replacement of wild-type tRNAPyl for future ncAA incorporation by PylRS enzymes.

Mitochondrial A12308G alteration in tRNALeu(CUN) in colorectal cancer samples

BackgroundColorectal cancer is the third most common type of cancer in men and women and the second leading cause of cancer-related deaths in the United States and UK. Colorectal cancer is strongly related to age, with almost three-quarters of cases occurring in people aged 65 or over. Pre-symptomatic screening is one of the most powerful tools for preventing colorectal cancer. Recently, the use of mitochondrial tRNA genes mutation or polymorphism patterns as a biomarker is rapidly expanding in different cancers because tRNA genes perform several functions including processing and translation which are essential components of mitochondrial protein synthesis. The aim of the present study was to find out the association of mitochondrial A12308G alteration in tRNALeu(CUN) in colorectal cancer and its usage as a new biomarker screening test.MethodsA tumor tissues from 30 patients who had colorectal cancer were selected randomly. The A12308G alteration in tRNALeu (CUN) was screened in the 30 colorectal tumor tissues. For comparison, 100 blood samples of healthy controls using PCR-sequencing methods were selected and the following results were found.ResultThe A12308G, a polymorphic mutation in V-loop tRNALeu(CUN), was found in 6 Colorectal tumor tissues and 3 healthy controls. A statistical significant difference was found between cases and control regarding the association of the A12308G mutation with the colorectal tumor (P < 0.05).ConclusionsThe A12308G, a polymorphic mutation in V-loop tRNALeu(CUN), could be considered as pathogenic mutation in combination with mitochondrial external conditions and other mitochondrial genes in developing different diseases especially cancers and could be used as one of the diagnostic tool. Also it seems that maybe there is relevance between A12308G mutation and other mutations that it can cause various phenotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s13000-015-0337-6) contains supplementary material, which is available to authorized users.

Impaired protein translation in Drosophila models for Charcot-Marie-Tooth neuropathy caused by mutant tRNA synthetases.

Dominant mutations in five tRNA synthetases cause Charcot–Marie–Tooth (CMT) neuropathy, suggesting that altered aminoacylation function underlies the disease. However, previous studies showed that loss of aminoacylation activity is not required to cause CMT. Here we present a Drosophila model for CMT with mutations in glycyl-tRNA synthetase (GARS). Expression of three CMT-mutant GARS proteins induces defects in motor performance and motor and sensory neuron morphology, and shortens lifespan. Mutant GARS proteins display normal subcellular localization but markedly reduce global protein synthesis in motor and sensory neurons, or when ubiquitously expressed in adults, as revealed by FUNCAT and BONCAT. Translational slowdown is not attributable to altered tRNAGly aminoacylation, and cannot be rescued by Drosophila Gars overexpression, indicating a gain-of-toxic-function mechanism. Expression of CMT-mutant tyrosyl-tRNA synthetase also impairs translation, suggesting a common pathogenic mechanism. Finally, genetic reduction of translation is sufficient to induce CMT-like phenotypes, indicating a causal contribution of translational slowdown to CMT.

The tRNA(Gly) T10003C mutation in mitochondrial haplogroup M11b in a Chinese family with diabetes decreases the steady-state level of tRNA(Gly), increases aberrant reactive oxygen species production, and reduces mitochondrial membrane potential.

Mitochondrial diabetes originates mainly from mutations located in maternally transmitted, mitochondrial tRNA-coding genes. In a genetic screening program of type 2 diabetes conducted with a Chinese Han population, we found one family with suggestive maternally transmitted diabetes. The proband's mitochondrial genome was analyzed using DNA sequencing. Total 42 known nucleoside changes and 1 novel variant were identified, and the entire mitochondrial DNA sequence was assigned to haplogroup M11b. Phylogenetic analysis showed that a homoplasmic mutation, 10003T>C transition, occurred at the highly conserved site in the gene encoding tRNA(Gly). Using a transmitochondrial cybrid cell line harboring this mutation, we observed that the steady-state level of tRNA(Gly) significantly affected and the amount of tRNA(Gly) decreased by 97%, production of reactive oxygen species was enhanced, and mitochondrial membrane potential, mtDNA copy number and cellular oxygen consumption rate were remarkably decreased compared with wild-type cybrid cells. The homoplasmic 10003T>C mutation in the mitochondrial tRNA(Gly) gene suggested to be as a pathogenesis-related mutation which might contribute to the maternal inherited diabetes in the Han Chinese family.

Simultaneous DNA and RNA Mapping of Somatic Mitochondrial Mutations across Diverse Human Cancers.

Somatic mutations in the nuclear genome are required for tumor formation, but the functional consequences of somatic mitochondrial DNA (mtDNA) mutations are less understood. Here we identify somatic mtDNA mutations across 527 tumors and 14 cancer types, using an approach that takes advantage of evidence from both genomic and transcriptomic sequencing. We find that there is selective pressure against deleterious coding mutations, supporting that functional mitochondria are required in tumor cells, and also observe a strong mutational strand bias, compatible with endogenous replication-coupled errors as the major source of mutations. Interestingly, while allelic ratios in general were consistent in RNA compared to DNA, some mutations in tRNAs displayed strong allelic imbalances caused by accumulation of unprocessed tRNA precursors. The effect was explained by altered secondary structure, demonstrating that correct tRNA folding is a major determinant for processing of polycistronic mitochondrial transcripts. Additionally, the data suggest that tRNA clusters are preferably processed in the 3′ to 5′ direction. Our study gives insights into mtDNA function in cancer and answers questions regarding mitochondrial tRNA biogenesis that are difficult to address in controlled experimental systems.

Identification of determinants for tRNA substrate recognition by Escherichia coli C/U34 2′-O-methyltransferase

Post-transcriptional modifications bring chemical diversity to tRNAs, especially at positions 34 and 37 of the anticodon stem-loop (ASL). TrmL is the prokaryotic methyltransferase that catalyzes the transfer of the methyl group from S-adenosyl-L-methionine to the wobble base of tRNALeuCAA and tRNALeuUAA isoacceptors. This Cm34/Um34 modification affects codon-anticodon interactions and is essential for translational fidelity. TrmL-catalyzed 2′-O-methylation requires its homodimerization; however, understanding of the tRNA recognition mechanism by TrmL remains elusive. In the current study, by measuring tRNA methylation by TrmL and performing kinetic analysis of tRNA mutants, we found that TrmL exhibits a fine-tuned tRNA substrate recognition mechanism. Anticodon stem-loop minihelices with an extension of 2 base pairs are the minimal substrate for EcTrmL methylation. A35 is a key residue for TrmL recognition, while A36-A37-A38 are important either via direct interaction with TrmL or due to the necessity for prior isopentenylation (i6) at A37. In addition, TrmL only methylates pyrimidines but not purine residues at the wobble position, and the 2′-O-methylation relies on prior N6-isopentenyladenosine modification at position 37.

The Structure of Escherichia coli TcdA (Also Known As CsdL) Reveals a Novel Topology and Provides Insight into the tRNA Binding Surface Required for N6-Threonylcarbamoyladenosine Dehydratase Activity

Escherichia coli TcdA (also known as CsdL) was previously shown to catalyze the ATP-dependent dehydration/cyclization of hypermodified tRNA N6-threonylcarbamoyladenosine into further cyclic N6-threonylcarbamoyladenosine. In this study, we report the X-ray crystal structures of E. coli TcdA with either AMP or ATP bound. The AMP/ATP-bound N-terminal sub-domain of TcdA resembles the ATP-binding Rossmann fold of E. coli ThiF and MoeB that are enzymes respectively taking part in the biosynthesis of thiamine and molybdopterin; however, the remaining C-terminal sub-domain of TcdA adopts a structure unrelated to any other known folds. In TcdA, the ATP-utilizing adenylation of tRNA N6-threonylcarbamoyladenosine and a subsequent thioester formation via an active cysteine, similar to the mechanisms in ThiF and MoeB, could take place for the dehydratase function. Analysis of the structure with sequence alignment suggests the disordered Cys234 of TcdA as the most likely catalytic residue. The structure further indicates that the C-terminal sub-domain can provide a binding interface for the tRNA substrate. Binding study using the surface mutants of TcdA and tRNA reveals that the positively charged regions of mainly the C-terminal sub-domain are important for the tRNA recognition.

Is the cellular initiation of translation an exclusive property of the initiator tRNAs?

Translation of mRNAs is the primary function of the ribosomal machinery. Although cells allow for a certain level of translational errors/mistranslation (which may well be a strategic need), maintenance of the fidelity of translation is vital for the cellular function and fitness. The P-site bound initiator tRNA selects the start codon in an mRNA and specifies the reading frame. A direct P-site binding of the initiator tRNA is a function of its special structural features, ribosomal elements, and the initiation factors. A highly conserved feature of the 3 consecutive G:C base pairs (3GC pairs) in the anticodon stem of the initiator tRNAs is vital in directing it to the P-site. Mutations in the 3GC pairs diminish/abolish initiation under normal physiological conditions. Using molecular genetics approaches, we have identified conditions that allow initiation with the mutant tRNAs in Escherichia coli. During our studies, we have uncovered a novel phenomenon of in vivo initiation by elongator tRNAs. Here, we recapitulate how the cellular abundance of the initiator tRNA, and nucleoside modifications in rRNA are connected with the tRNA selection in the P-site. We then discuss our recent finding of how a conserved feature in the mRNA, the Shine-Dalgarno sequence, influences tRNA selection in the P-site.

Mitochondrial tRNASer(UCN) variants in 2651 Han Chinese subjects with hearing loss

Mutations in the mitochondrial DNA have been associated with hearing loss. However, the prevalence and spectrum of mitochondrial tRNA mutations in hearing-impaired subjects are poorly understood. In this report, we have investigated the prevalence and spectrum of mitochondrial tRNASer(UCN) mutations in a large cohort of 2651 Han Chinese subjects with hearing loss. The clinical evaluation showed that 744 subjects (432 males and 312 females) had a history of exposure to aminoglycosides and other probands exhibited nonsyndromic hearing loss. Mutational analysis of tRNASer(UCN) gene identified 9 (8 known and 1 novel) variants. The prevalence of the known deafness-associated 7511T>C, 7505T>C and 7445A>C mutations was 0.04%, 0.04% and 0.04%, respectively. Other variants were evaluated by the evolutionary conservation, allelic frequency of Chinese controls, potential structural and functional alterations and pedigree analysis. Three variants were polymorphisms, while the 7444G>A, 7471DelG and 7496A>G variants were putative deafness-associated mutations. These putative deafness-associated variants accounted for 0.68% cases of hearing-impaired subjects in this cohort. The low penetrance of hearing loss in pedigrees carrying one of these putative deafness-associated mutations indicated that the mutation(s) is necessary but itself insufficient to produce a clinical phenotype. Other genetic or environmental factor(s) may influence the phenotypic manifestation of these tRNASer(UCN) mutations. Moreover, mtDNAs in 20 probands carrying one of the putative deafness-associated mutations were widely dispersed among 8 Eastern Asian haplogroups. In particular, the occurrences of haplogroups D4a, M22, and H2 in patients carrying the deafness-associated variants were higher than those in Chinese controls. These data further support that the mitochondrial tRNASer(UCN) gene is the hot spot for mutations associated with hearing loss. Thus, our findings may provide valuable information for the further understanding of pathophysiology and management of hearing loss.

Expanding the Genetic Code with Pyroglutamate

Pyroglutamate (pGlu) is an amino acid found in a number of proteins including amyloid b-peptides associated with Alzheimer's disease and oconase, an anti-cancer agent. It forms via post-translational modifications of N-terminal glutamine (Gln) or glutamate (Glu) residues via cyclization. To facilitate research into the function of pGlu, we are expanding the genetic code of E. coli to include the modified amino acid via an amber suppressor system. To add pGlu to the code, we modified the archaeal RNA-dependent Gln biosynthetic pathway using a glutamyl-tRNA synthetase and the amidotransferase GatDE to synthesizepGlu on a mutant archaeal amber suppressor tRNA (tRNApGlu). The system is orthogonal in E. coli. The relevant genes were cloned into a pRSF-Duet vector and transformed into E. coli to determine if they can form pGlu-tRNApGlu in vivo. Read-through of an amber codon in a genetic message is being verified using an enhanced yellow fluorescence protein (eYFP) reporter system. Site-specific incorporation of pGlu into the protein will be validated by mass-spectrometry. Once established, we will use the system to test the role of the amino acid in RNaseA. This work was supported by a Research Corporation Cottrell College Science Award and Skidmore College.

Glutamine tRNA CUG ‐Dependent, Nitrogen‐Responsive Nuclear Gln3 and Gat1 Localization

A leucine-dependent pathway activates TorC1 kinase and its downstream stimulation of protein synthesis. However, Gln3 and Gat1, nitrogen-responsive transcription activators, don't respond to leucine-dependent TorC1 activation. This led us to conclude that excess nitrogen-dependent down regulation of Gln3 occurs via a second mechanism. A major site of Gln3/Gat1 control occurs at their access to the nucleus. In excess nitrogen, Gln3/Gat1 are sequestered in the cytoplasm in a Ure2-dependent manner. They become nuclear when nitrogen or glutamine is limiting. The sensitivity of Gln3 localization to glutamine and inhibition of glutamine synthesis by methionine sulfoximine (Msx) prompted us to investigate the effects of a glutamine tRNA mutation (sup70-65) on Gln3/Gat1 regulation. Contrary to prediction, we show nuclear Gln3 localization - elicited by short- and long-term nitrogen starvation, growth in proline, during Msx or rapamycin treatment or in a ure2Δ - is abolished by alteration of glutamine tRNACUG. In contrast, nuclear Gat1 localization, which also exhibits a glutamine tRNACUG requirement for its response to short-term nitrogen starvation, growth in proline medium or a ure2Δ, neither responds to Msx or long-term starvation nor requires tRNACUG for its response to rapamycin. Gln3/Gat1 requirements for the rare tRNACUG, cannot be replaced in growing cells by the predominant glutamine tRNACAA. These observations demonstrate the existence of a specific nitrogen-responsive component participating in the control of Gln3/Gat1 localization that is highly sensitive to the function of the rare glutamine tRNACUG. Our data also demonstrate distinct mechanistic differences between the regulation of Gln3 and Gat1. Supported by NIH grant GM-35642.

Mitochondrial tRNA mutations in patients with myelodysplastic syndromes

Increasing evidence showed that mitochondria play an important role in the development of myelodysplastic syndromes (MDS). Mitochondrial dysfunctions caused by mitochondrial DNA mutations, especially mitochondrial tRNA mutations, were found to be associated with MDS in many studies. However, the link between a candidate mitochondrial tRNA mutation and MDS was not clear. In this study, we investigated the role of some mitochondrial tRNA mutations, and their deleterious roles were further discussed.

The mitochondrial tRNAGln T4353C mutation may not be associated with essential hypertension in Han Chinese population

We reported here the possible role of a mitochondrial tRNA mutation: T4353C in clinical expression of essential hypertension in Chinese population. The human mammalian mitochondrial tRNA database was used to analyze the conservation index of this mutation between different species. Moreover, phylogenetic analysis showed that the T4353C mutation belonged to human mitochondrial haplogroup HV, a West Eurasian haplogroup found throughout Western Asia and Eastern European but was infrequent in China. In addition, structural prediction of the T4353C mutation indicated that this transition did not alter the secondary structure of tRNAGln. Together, our data indicated that the T4353C mutation occurred infrequent and may not be associated with essential hypertension in Han Chinese population.

Maternally inherited diabetes is associated with a homoplasmic T10003C mutation in the mitochondrial tRNAGly gene

In this report, we investigate molecular pathogenic mechanism of a diabetes-associated homoplasmic mitochondrial tRNA mutation in a Han Chinese family with maternally transmitted diabetes mellitus. Of 10 adult matrilineal relatives, 5 individuals suffered from diabetes (4 subjects with only diabetes, one subject with both diabetes and hearing impairment), while other five matrilineal relatives (one with hearing loss) had glucose intolerance. The average age at onset of diabetes in matrilineal relatives was 50years. Molecular analysis of their mitochondrial genomes identified the novel homoplasmic T10003C mutation in the tRNAGly gene belonging to haplogroup M11b. The T10003C mutation is expected to form a base-pairing (13C-22G) at the highly conserved D-stem of tRNAGly, thereby affecting secondary structure and function of this tRNA. A tRNA Northern analysis revealed that the T10003C mutation caused ~70% reduction in the steady-state level of tRNAGly. An in vivo translation analysis showed ~33% reduction in the rate of mitochondrial translation in mutant cells. Oxygen consumption analysis showed the defects in overall respiratory capacity or the ATP-linked, proton leak, and maximal respiration in mutant cells. As a result, the cellular energy deficiency contributes to the development of diabetes in subjects carrying the T10003C mutation. These data provide the first direct evidence that the tRNAGly mutation might be associated with diabetes. Thus, our findings may provide new insights into the understanding of pathophysiology of maternally inherited diabetes.

Mitochondrial transfer RNA mutations and hypertension.

Mutations in mitochondrial DNA have been found to be associated with hypertension. Of these, mitochondrial transfer RNA (mt-tRNA) is a hot spot for these pathogenic mutations. It is generally believed that these mutations may result in the failure of mt-tRNA metabolism, thereby worsening mitochondrial dysfunction and resulting in hypertension. mt-tRNA is known for its high frequency of polymorphisms and mutations, and the number of reports regarding mt-tRNA mutations and hypertension is increasing significantly. To better understand the molecular basis of maternally inherited hypertension, we reassessed the link between four mt-tRNA mutations (G15927A in tRNA(Thr), C7492T in tRNA(Ser(UCN)), A4386G in tRNA(Gln), and C14686T in tRNA(Glu)) and hypertension. We first used the phylogenetic approach to investigate the deleterious roles of these mutations, then we used RNA Fold Web Server to predict the minimum free energy of these mt-tRNAs with and without mutations. Using the pathogenicity scoring system, we found that the G15927A and C7492T mutations are classified as pathogenic while all other studied mutations are neutral polymorphisms. Our study provides valuable information for the detection of pathogenic mt-tRNA mutations in hypertension.

Emerging roles of tRNA in adaptive translation, signalling dynamics and disease.

tRNAs, nexus molecules between mRNAs and proteins, have a central role in translation. Recent discoveries have revealed unprecedented complexity of tRNA biosynthesis, modification patterns, regulation and function. In this Review, we present emerging concepts regarding how tRNA abundance is dynamically regulated and how tRNAs (and their nucleolytic fragments) are centrally involved in stress signalling and adaptive translation, operating across a wide range of timescales. Mutations in tRNAs or in genes affecting tRNA biogenesis are also linked to complex human diseases with surprising heterogeneity in tissue vulnerability, and we highlight cell-specific aspects that modulate the disease penetrance of tRNA-based pathologies.

Nitrogen starvation and TorC1 inhibition differentially affect nuclear localization of the Gln3 and Gat1 transcription factors through the rare glutamine tRNACUG in Saccharomyces cerevisiae.

A leucine, leucyl-tRNA synthetase-dependent pathway activates TorC1 kinase and its downstream stimulation of protein synthesis, a major nitrogen consumer. We previously demonstrated, however, that control of Gln3, a transcription activator of catabolic genes whose products generate the nitrogenous precursors for protein synthesis, is not subject to leucine-dependent TorC1 activation. This led us to conclude that excess nitrogen-dependent down-regulation of Gln3 occurs via a second mechanism that is independent of leucine-dependent TorC1 activation. A major site of Gln3 and Gat1 (another GATA-binding transcription activator) control occurs at their access to the nucleus. In excess nitrogen, Gln3 and Gat1 are sequestered in the cytoplasm in a Ure2-dependent manner. They become nuclear and activate transcription when nitrogen becomes limiting. Long-term nitrogen starvation and treatment of cells with the glutamine synthetase inhibitor methionine sulfoximine (Msx) also elicit nuclear Gln3 localization. The sensitivity of Gln3 localization to glutamine and inhibition of glutamine synthesis prompted us to investigate the effects of a glutamine tRNA mutation (sup70-65) on nitrogen-responsive control of Gln3 and Gat1. We found that nuclear Gln3 localization elicited by short- and long-term nitrogen starvation; growth in a poor, derepressive medium; Msx or rapamycin treatment; or ure2Δ mutation is abolished in a sup70-65 mutant. However, nuclear Gat1 localization, which also exhibits a glutamine tRNACUG requirement for its response to short-term nitrogen starvation or growth in proline medium or a ure2Δ mutation, does not require tRNACUG for its response to rapamycin. Also, in contrast with Gln3, Gat1 localization does not respond to long-term nitrogen starvation. These observations demonstrate the existence of a specific nitrogen-responsive component participating in the control of Gln3 and Gat1 localization and their downstream production of nitrogenous precursors. This component is highly sensitive to the function of the rare glutamine tRNACUG, which cannot be replaced by the predominant glutamine tRNACAA. Our observations also demonstrate distinct mechanistic differences between the responses of Gln3 and Gat1 to rapamycin inhibition of TorC1 and nitrogen starvation.

Reversible infantile mitochondrial diseases.

Mitochondrial diseases are usually severe and progressive conditions; however, there are rare forms that show remarkable spontaneous recoveries. Two homoplasmic mitochondrial tRNA mutations (m.14674T>C/G in mt-tRNA(Glu)) have been reported to cause severe infantile mitochondrial myopathy in the first months of life. If these patients survive the first year of life by extensive life-sustaining measures they usually recover and develop normally. Another mitochondrial disease due to deficiency of the 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) causes severe liver failure in infancy, but similar to the reversible mitochondrial myopathy, within the first year of life these infants may also recover completely. Partial recovery has been noted in some other rare forms of mitochondrial disease due to deficiency of mitochondrial tRNA synthetases and mitochondrial tRNA modifying enzymes. Here we summarize the clinical presentation of these unique reversible mitochondrial diseases and discuss potential molecular mechanisms behind the reversibility. Understanding these mechanisms may provide the key to treatments of potential broader relevance in mitochondrial disease, where for the majority of the patients no effective treatment is currently available.

Effect of mitochondrial tRNALys mutation on the clinical and biochemical characteristics of Chinese essential hypertensive subjects

Mitochondrial dysfunction has been potentially implicated in both human and experimental hypertension. We performed the mutational analysis of tRNALys gene by PCR amplification and subsequent sequence analysis of the PCR fragments from 990 Chinese essential hypertensive subjects. We also made a comparative analysis of the collected data of the essential hypertension subjects who carried tRNALys mutation and those who did not carry the mutation using the methods of 1:1 case-control study. We totally found 7 mutation sites in 10 subjects. The onset ages of the individuals carrying the mutation were earlier than those who did not bear them. The level of blood urea nitrogen in hypertension subjects who carried tRNALys mutation was higher than the hypertension subjects who did not carried tRNALys mutation, while the serum potassium was significantly lower. The level of platelet count in hypertension subjects who carried tRNALys mutation was lower. The level of ventricular septal thickness in hypertension subjects who carried tRNALys mutation was higher and the level of left ventricular end diastolic diameter in hypertension subjects was significantly lower. Mitochondrial tRNALys mutations might result in the change of their structure and function, and then damaged the blood metabolism, the balance of the blood electrolyte, the steady-state of the blood cells and the heart structure and function, which were involved in the progress of the essential hypertension. Part of the essential hypertension patients clinically presented the characters of maternal inheritance, which might be associated with the tRNALys mutation.