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At least 469 records · Page 26Linked to original sources
PubMed1993

Two Streptomyces lividans 66 transfer RNA genes with anticodons corresponding to serine (AGC) and arginine (CGU) codons.

From the nucleotide sequence of a 2110-bp Streptomyces lividans 66 DNA fragment two transfer RNA genes were identified: tRNA(Ser) (AGC) and tRNA(Arg) (CGU). These tRNA genes are transcribed from the same DNA strand and both are preceded by a putative promoter structure. They are separated by an intergenic region of 191 bp. Like most Streptomyces tRNA genes described so far, they do not encode the 3' terminal CCA of mature tRNAs. Both genes are followed by extensive inverted repeats, which could serve as transcriptional terminator signals. Remarkably, these hairpin structures share an identical 9 base pair stretch (5'-GAAGCCCCG-3'). Furthermore, the tRNA(Arg) region is followed by two potential open reading frames, which are encoded on complementary strands and have 3' overlapping ends. The gene for tRNA(Arg) (CGU) is the first Streptomyces tRNA gene described so far which encodes the translation of a codon with uridine at the third (wobble) position.

Anticodon↗
PubMed1999

An engineered class I transfer RNA with a class II tertiary fold.

Structure-based engineering of the tertiary fold of Escherichia coli tRNA(Gln)2 has enabled conversion of this transfer RNA to a class II structure while retaining recognition properties of a class I glutamine tRNA. The new tRNA possesses the 20-nt variable stem-loop of Thermus thermophilus tRNA(Ser). Enlargement of the D-loop appears essential to maintaining a stable tertiary structure in this species, while rearrangement of a base triple in the augmented D-stem is critical for efficient glutaminylation. These data provide new insight into structural determinants distinguishing the class I and class II tRNA folds, and demonstrate a marked sensitivity of glutaminyl-tRNA synthetase to alteration of tRNA tertiary structure.

Acylation↗
PubMed2006

Archaeology and evolution of transfer RNA genes in the Escherichia coli genome.

Transfer RNA genes tend to be presented in multiple copies in the genomes of most organisms, from bacteria to eukaryotes. The evolution and genomic structure of tRNA genes has been a somewhat neglected area of molecular evolution. Escherichia coli, the first phylogenetic species for which more than two different strains have been sequenced, provides an invaluable framework to study the evolution of tRNA genes. In this work, a detailed analysis of the tRNA structure of the genomes of Escherichia coli strains K12, CFT073, and O157:H7, Shigella flexneri 2a 301, and Salmonella typhimurium LT2 was carried out. A phylogenetic analysis of these organisms was completed, and an archaeological map depicting the main events in the evolution of tRNA genes was drawn. It is shown that duplications, deletions, and horizontal gene transfers are the main factors driving tRNA evolution in these genomes. On average, 0.64 tRNA insertions/duplications occur every million years (Myr) per genome per lineage, while deletions occur at the slower rate of 0.30 per million years per genome per lineage. This work provides a first genomic glance at the problem of tRNA evolution as a repetitive process, and the relationship of this mechanism to genome evolution and codon usage is discussed.

Codon↗
PubMed2001

A new mitochondrial point mutation in the transfer RNA(Leu) gene in a patient with a clinical phenotype resembling Kearns-Sayre syndrome.

OBJECTIVE: To report on the molecular identification of a novel heteroplasmic G-to-A transition at mitochondrial DNA position 3249 in transfer RNA(Leu) gene in a patient with a clinical phenotype resembling Kearns-Sayre syndrome. PATIENT AND METHODS: A 34-year-old patient had been suffering for more than 10 years from progressive visual failure, neurosensorial hearing loss, exercise intolerance, muscle weakness, paresthesia in the lower limbs, and difficulties swallowing. Clinical examination revealed generalized muscle wasting, ptosis, external ophthalmoplegia, and ataxia. Ophthalmologic examination showed dystrophic features in the cornea and retina. In skeletal muscle, morphologic and biochemical studies of the respiratory chain complexes were performed. Polymerase chain reaction, single-strand conformation polymorphism, and direct sequencing were used to screen for mutations in the 22 mitochondrial transfer RNA genes. RESULTS: In skeletal muscle, a significantly decreased catalytic activity of complex I was detected by spectrophotometric analysis and numerous cytochrome c oxidase-negative ragged-red fibers were seen on morphologic examination. A G-to-A substitution 3249 (G3249A) mutation was found in the transfer RNA(Leu) gene of the patient and mutant mitochondrial DNA represented 85% of the total in skeletal muscle but only 45% in leukocytes. The mutation was shown to be present in a small fraction in leukocytes from the unaffected mother and to be absent in leukocytes from the healthy sister. CONCLUSIONS: A causal relationship between a heteroplasmic G3249A transfer RNA(Leu) mutation in a patient suffering from progressive external ophthalmoplegia, retinal dystrophy, ataxia, neurosensorial hearing loss, and muscle wasting is postulated. To our knowledge, the G3249A mutation has never previously been described and was not detected in control subjects.

Adult↗
PubMed1986

Hydrophobic interaction chromatography of incompletely methylated transfer RNA from Escherichia coli on octyl-sepharose.

Phenylalanine-specific transfer RNA from methionine-starved relaxed Escherichia coli K12 separates into two components when chromatographed on Octyl-Sepharose. The difference in elution between the two tRNAs has been shown to depend on the methyl group in the highly modified 2-methylthio-N-6-isopentenyladenosine. The first eluted tRNAPhe lacks this methyl group, while the last eluted tRNAPhe is fully methylated. Other differences in the modification patterns have no effect on the elution from Octyl-Sepharose. The elution pattern of tyrosine- and serine-specific tRNAs, also normally containing ms2i6A, is similar.

Amino Acyl-tRNA Synthetases↗
PubMed1975

The distribution and properties of aspartyl transfer RNA in human and animal tumors.

The elution profile of aspartyl transfer RNA (aspartyl-tRNA) from reversed phase 5 chromatography for tRNA from a spectrum of animal tissues and tumors and human tumors has been examined. It was found that SV40-induced hamster tumors, BHK21/cl 13 cells in culture, certain carcinogen-induced tumors in the Ehrlich ascites tumor, and a number of human carcinomas and adenocarcinomas contained a distinct increase (3- to 20-fold) in the percentage of a late-eluting aspartyl-tRNA over that found in nonmalignant tissues, other animal tumors, and in human melanomas and sarcomas. The ability of the late-eluting aspartyl-tRNAAspIV to bind to ribosomes in the presence of the codons for aspartic acid was compared to that of aspartyl-tRNAAspIII and was found to be approximately the same. Also, the ability of each of the 4 isoaccepting species of aspartyl-tRNA to engage in ribosomal incorporation of aspartic acid into a polypeptide was determined. All 4 isoacceptors function equally well in the amino acid incorporation.

Adenocarcinoma↗
PubMed1978

Identification of an Escherichia coli nuclease acting on structurally altered transfer RNA molecules.

A nuclease (RNase D) that can recognize structurally altered transfer RNA molecules has been partially purified from Escherichia coli. The enzyme acts poorly on intact tRNA and is inactive with the synthetic polyribonucleotides, poly(A), poly(U), or double-stranded poly(A).poly(U). The enzyme requires Mg2+ for activity and is stimulated by the monovalent cations, K+ and NH4+. The products of the reaction are 5'-mononucleotides. The molecular weight of the protein is about 60,000 as judged by Sephadex G-100 chromatography. The enzyme does not correspond to any known E. coli ribonuclease and may represent an intracellular scavenging mechanism for denatured tRNAs and other inactive RNA molecules.

Cations↗
PubMed1985

RNA processing in Neurospora crassa mitochondria: use of transfer RNA sequences as signals.

We have used RNA gel transfer hybridization, S1 nuclease mapping and primer extension to analyze transcripts derived from several genes in Neurospora crassa mitochondria. The transcripts studied include those for cytochrome oxidase subunit III, 17S rRNA and an unidentified open reading frame. In all three cases, initial transcripts are long, include tRNA sequences, and are subsequently processed to generate the mature RNAs. We find that endpoints of the most abundant transcripts generally coincide with those of tRNA sequences. We therefore conclude that tRNA sequences in long transcripts act as primary signals for RNA processing in N. crassa mitochondria. The situation is somewhat analogous to that observed in mammalian mitochondrial systems. The difference, however, is that in mammalian mitochondria, noncoding spacers between tRNA, rRNA and protein genes are very short and in many cases non-existent, allowing no room for intergenic RNA processing signals whereas, in N. crassa mtDNA, intergenic non-coding sequences are usually several hundred nucleotides long and contain highly conserved GC-rich palindromic sequences. Since these GC-rich palindromic sequences are retained in the processed mature RNAs, we conclude that they do not serve as signals for RNA processing.

Base Sequence↗
PubMed1997

UKPDS 21: low prevalence of the mitochondrial transfer RNA gene (tRNA(Leu(UUR))) mutation at position 3243bp in UK Caucasian type 2 diabetic patients.

Some patients with Type 2 (non-insulin-dependent) diabetes mellitus possess a mitochondrial mutation in the tRNA(Leu(UUR)) gene at position 3243 bp. These subjects show a maternal mode of inheritance and often have hearing defects. In French and Japanese populations, this mutation may be present in 1-3% of subjects with a family history of diabetes. We assessed the prevalence of this mutation in newly diagnosed diabetic subjects in the UK white Caucasian population. The 3243 bp mutation was not detected in 500 randomly selected Type 2 diabetic subjects, 50 gestational diabetic subjects, and members of a MODY pedigree. Two of 748 (0.27%) Type 2 diabetic subjects with a family history of diabetes were found to possess the mutation. These subjects had an early age of diagnosis (M 38 years; F 36 years) and were non-obese. The male patient showed evidence of markedly impaired beta-cell function and deafness, while the female was not deaf, had approximately 50% of normal pancreatic function and responded well to diet. The mutation in the tRNA(Leu(UUR)) gene probably occurs in only approximately 0.1-0.2% of white Caucasian Type 2 diabetic patients in the UK.

Adult↗