Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q96FX7 (tRNA)
 26,753 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Temperature-sensitive mutants of Saccharomyces cerevisiae were isolated by insertional mutagenesis using the HIS3 marked retrotransposon TyH3HIS3. In such mutants, the TyHIS3 insertions are expected to identify loci which encode genes essential for cell growth at high temperatures but dispensable at low temperatures. Five mutations were isolated and named hit for high temperature growth. The hit1-1 mutation was located on chromosome X and conferred the pet phenotype. Two hit2 mutations, hit2-1 and hit2-2, were located on chromosome III and caused the deletion of the PET18 locus which has been shown to encode a gene required for growth at high temperatures. The hit3-1 mutation was located on chromosome VI and affected the CDC26 gene. The hit4-1 mutation was located on chromosome XIII. These hit mutations were analyzed in an attempt to identify novel genes involved in the heat shock response. The hit1-1 mutation caused a defect in synthesis of a 74-kD heat shock protein. Western blot analysis revealed that the heat shock protein corresponded to the SSC1 protein, a member of the yeast hsp70 family. In the hit1-1 mutant, the TyHIS3 insertion caused a deletion of a 3-kb DNA segment between the delta 1 and delta 4 sequences near the SUP4 locus. The 1031-bp wild-type HIT1 DNA which contained an open reading frame encoding a protein of 164 amino acids and the AGG arginine tRNA gene complemented all hit1-1 mutant phenotypes, indicating that the mutant phenotypes were caused by the deletion of these genes. The pleiotropy of the HIT1 locus was analyzed by constructing a disruption mutation of each gene in vitro and transplacing it to the chromosome. This analysis revealed that the HIT1 gene essential for growth at high temperatures encodes the 164-amino acid protein. The arginine tRNA gene, named HSX1, is essential for growth on a nonfermentable carbon source at high temperatures and for synthesis of the SSC1 heat shock protein.
 ...
PMID:Ty element-induced temperature-sensitive mutations of Saccharomyces cerevisiae. 132 86

It has been shown that tandems of rare arginine codons AGG have a strong inhibitory effect on translation of mRNA in E. coli [5]. This has been explained by the rate-limiting interaction of these codons with the less abundant tRNA(AGG) [6]. In this study tandemly repeated AGG triplets were introduced into the chloramphenicol acetyltransferase (CAT) gene either upstream of the initiation ATG codon or downstream of it (both in frame and out of frame) and the expression of the modified genes was investigated. We report that the addition of AGG clusters resulted in a substantial inhibitory effect on CAT gene expression independently of their localization in mRNA. This inhibitory effect is explained by a competition of the tandem AGGAGG with the natural Shine-Dalgarno (SD) sequence (consensus AAGGAGGU) for the 3'-end of the 16S small ribosomal RNA (rRNA).
 ...
PMID:Effect of tandemly repeated AGG triplets on the translation of CAT-mRNA in E. coli. 137 38

Influence of increased arginine concentrations of tRNA's corresponding to rare codons AGG and AGA was studied in the model system constructed earlier. The model system is a chimeric gene consisting of CAT gene fragment, part of the gene encoding for alpha-domain of beta-galactosidase E. coli and a series of synthetic inserts enriched with codons AGG and AGA. In order to increase the intracellular tRNA concentration the natural gene of AGA-specific tRNA and the artificial gene of AGG-specific tRNA were cloned in plasmid under the control of p15A ori compatible with co1EI ori and used for maintaining the model gene. It was shown that the artificial AGG-specific tRNA gene produces a functionally active tRNA. A steep rise in the synthesis of polypeptide encoded by the model template containing rare codons was demonstrated when the genes of tRNAs recognizing these codons were propagated in the multicopy plasmid. It was shown that AGA-specific tRNA efficiently translates both AGA and AGG codons while AGG-specific tRNA - only AGG codons.
 ...
PMID:[The effect of intracellular concentrations of tRNA, corresponding to the rare arginine codons AGG and AGA, on the gene expression in Escherichia coli]. 147 Jan 74

A recombinant Escherichia coli strain was constructed for the overexpression of bovine placental lactogen (bPL), using a bPL structural gene containing 9 of the rare arginine codons AGA and AGG. When high level bPL synthesis was induced in this strain, cell growth was inhibited and bPL accumulated to less than 10% of total cell protein. In addition, about 2% of the recombinant bPL produced from this strain exhibited an altered trypsin digestion pattern. Amino acid residues 74 through 109 normally produce 2 tryptic peptides, but the altered form of bPL lacked these two peptides and instead had a new peptide which was missing arginine residue 86 and one of the two flanking leucine residues. The codon for arginine residue 86 was AGG and the codons for the flanking leucine residues 85 and 87 were TTG. When 5 of the 9 AGA and AGG codons in the bPL structural gene were changed to more preferred arginine codons, cell growth was not inhibited and bPL accumulated to about 30% of total cell protein. When bPL was purified from this modified strain, which included changing the arginine codon at position 86 from AGG to CGT, none of the altered form of bPL was produced. These observations are consistent with a model in which translational pausing occurs at the arginine residue 86 AGG codon because the corresponding arginyl-tRNA species is reduced by the high level of bPL synthesis, and a translational hop occurs from the leucine residue 85 TTG codon to the leucine residue 87 TTG codon. This observation represents the first report of an error in protein synthesis due to an in-frame translational hop within an open reading frame.
 ...
PMID:Novel in-frame two codon translational hop during synthesis of bovine placental lactogen in a recombinant strain of Escherichia coli. 148 Apr 91

The supF gene of the shuttle vector pZ189 was used as a target for the study of mutations induced by cis-diamminedichloroplatinum(II) (cis-DDP). Normal human repair-proficient fibroblasts and cis-DDP repair-deficient xeroderma pigmentosum (XP) cells were used as host cells to study the effect of cis-DDP on the inhibition of shuttle vector replication and mutagenesis. Transfection of cis-DDP-treated pZ189 into normal and XP cell lines resulted in a marked increase in the mutation frequency and a decrease in the replication efficiency of the vector. However, these effects were much greater for the plasmid propagated in XP cells. Atomic absorption spectroscopy showed that six to eight Pt-DNA adducts per plasmid were necessary to inhibit plasmid replication by 50% in normal cells. In contrast, only one to two Pt-DNA adducts were necessary to inhibit replication of the plasmid by 50% in XP cells. Analysis of mutation sites demonstrated that cis-DDP treatment resulted primarily in single and double mutations separated by one base and limited to a few locations within the 85-bp mature tRNA. Propagation of the cis-DDP-treated vector in either normal or XP cells led to predominantly transversion mutations at AGA, AGG, and GAG sites and a cis-DDP-associated deletion of 174 bp. Although mutations occurred at target sites for cis-DDP adduct formation, there was no correlation between sites of mutation and the most frequent sites of adduct formation.
 ...
PMID:Spectrum of cis-diamminedichloroplatinum(II)-induced mutations in a shuttle vector propagated in human cells. 191 Apr 83

We argue that in animal mitochondria codon reassignments, such as those for AGA and AGG from arginine to serine or of AUA from isoleucine to methionine, are the result of an interplay between biased mutational forces and selective ones. In particular, there is a marked tendency for animal mitochondria to have very small genomes and to minimize their investment in components required for gene expression. These tendencies are expressed as a reduction in the diversity of tRNA isoacceptor species. In our view, the pressure to simplify tRNA populations, together with mutational bias against certain codons, will account for the codon reassignments observed in animal mitochondria. A parallel to the major codon bias in microorganisms, which likewise tends to reduce the diversity of the tRNA isoacceptor populations under fast growth conditions, may be drawn. Therefore, we suggest that codon reassignments are usefully viewed as an extreme form of codon bias.
 ...
PMID:An extreme codon preference strategy: codon reassignment. 192 8

AGA and AGG codons for arginine are the least used codons in Escherichia coli, which are encoded by a rare tRNA, the product of the dnaY gene. We examined the positions of arginine residues encoded by AGA/AGG codons in 678 E. coli proteins. It was found that AGA/AGG codons appear much more frequently within the first 25 codons. This tendency becomes more significant in those proteins containing only one AGA or AGG codon. Other minor codons such as CUA, UCA, AGU, ACA, GGA, CCC and AUA are also found to be preferentially used within the first 25 codons. The effects of the AGG codon on gene expression were examined by inserting one to five AGG codons after the 10th codon from the initiation codon of the lacZ gene. The production of beta-galactosidase decreased as more AGG codons were inserted. With five AGG codons, the production of beta-galactosidase (Gal-AGG5) completely ceased after a mid-log phase of cell growth. After 22 hr induction of the lacZ gene, the overall production of Gal-AGG5 was 11% of the control production (no insertion of arginine codons). When five CGU codons, the major arginine codon were inserted instead of AGG, the production of beta-galactosidase (Gal-CGU5) continued even after stationary phase and the overall production was 66% of the control. The negative effect of the AGG codons on the Gal-AGG5 production was found to be dependent upon the distance between the site of the AGG codons and the initiation codon. As the distance was increased by inserting extra sequences between the two codons, the production of Gal-AGG5 increased almost linearly up to 8 fold. From these results, we propose that the position of the minor codons in an mRNA plays an important role in the regulation of gene expression possibly by modulating the stability of the initiation complex for protein synthesis.
 ...
PMID:Suppression of the negative effect of minor arginine codons on gene expression; preferential usage of minor codons within the first 25 codons of the Escherichia coli genes. 210 7

Ribosomal frameshifting regulates expression of the TYB gene of yeast Ty retrotransposons. We previously demonstrated that a 14 nucleotide sequence conserved between two families of Ty elements was necessary and sufficient to support ribosomal frameshifting. This work demonstrates that only 7 of these 14 nucleotides are needed for normal levels of frameshifting. Any change to the sequence CUU-AGG-C drastically reduces frameshifting; this suggests that two specific tRNAs, tRNA(UAGLeu) and tRNA(CCUArg), are involved in the event. Our tRNA overproduction data suggest that a leucyl-tRNA, probably tRNA(UAGLeu), an unusual leucine isoacceptor that recognizes all six leucine codons, slips from CUU-Leu onto UUA-Leu (in the +1 reading frame) during a translational pause at the AGG-Arg codon induced by the low availability of tRNA(CCUArg), encoded by a single-copy essential gene. Frameshifting is also directional and reading frame specific. Interestingly, frameshifting is inhibited when the "slip" CUU codon is located three codons downstream, but not four or more codons downstream, of the translational initiation codon.
 ...
PMID:Ribosomal frameshifting in the yeast retrotransposon Ty: tRNAs induce slippage on a 7 nucleotide minimal site. 216 89

Arginine is coded for by CGN (N = G, A, U, C), AGA and AGG. In Escherichia coli there is little tRNA for AGA and AGG and the use of these codons is strongly avoided in virtually all genes. Recently, we demonstrated that the presence of tandem AGA or AGG codons in mRNA causes frameshifts with high frequency. Here, we show that phaseshifts can be suppressed when cells are transformed with the gene for tRNA(T4Arg) or E. coli tRNA(argU,Arg) demonstrating that such errors are the result of tRNA depletion. Bacteriophage T4 encoded tRNA(Arg) (anticodon UCU) corrects shifts at AGA-AGA but not at AGG-AGG, suggesting that this tRNA can only read AGA. Similarly, comparison of the translational efficiencies in an argU (Ts) mutant and in its isogenic wild type parent indicates that argU tRNA (anticodon UCU) reads AGA but not AGG. An argU (Ts) mutant barely reads through AGA-AGA at 42 degrees C but translation of AGG-AGG is hardly, if at all, affected. Overexpression of argU+ relaxes the codon specificity. The thermosensitive mutant in argU, previously called dnaY because it is defective in DNA replication, can be complemented for growth by the gene for tRNA(T4Arg). This implies that the sole function of the argU gene product is to sustain protein synthesis and that its role in replication is probably indirect.
 ...
PMID:Frameshift suppression at tandem AGA and AGG codons by cloned tRNA genes: assigning a codon to argU tRNA and T4 tRNA(Arg). 220 35

To test features of the current model of transcription attenuation in amino acid biosynthetic operons, alterations were introduced into the trp operon leader region and expression of the mutated operons was examined in miaA and miaA+ Escherichia coli strains that lacked the trp repressor. The miaA mutation prevents modification of the adenosine residue immediately 3' of the anticodon of tRNAs that interact with codons beginning with uridine. The undermodified tRNA(Trp) in miaA strains is thought to increase readthrough at the trp attenuator by slowing ribosome movement over two tandem Trp codons in the 14-codon leader peptide coding region. The rate of translation of these two "control codons" is thought to be the key step in determining the extent of transcription attenuation in the trp leader region. Sequential deletion of trpL DNA specifying the leader peptide initiation region, RNA segment 1, RNA segment 2 and RNA segment 3 alternately decreased and increased trp operon expression, a result consistent with previous findings in another bacterium and the generally accepted model for transcription attenuation. Replacement of the tandem Trp control codons by AGG-UGC (Arg-Cys) codons eliminated the miaA-dependent increase in transcription readthrough. Replacement of the Trp control codons by AGG-UGA (Arg-stop) codons caused complete readthrough at the trp attenuator as well as abolishing the miaA effect. Presumably, the ribosome terminating translation at the new UGA codon mimics the effect of a stalled ribosome at the Trp control codons. This finding suggests that ribosome dissociation at some stop codons is slow relative to the time required for transcription of the trp leader region. Thus, most ribosomes translating the trp leader peptide coding region may remain attached to the natural UGA stop codon until after the attenuation decision is made. The interpretation supports models for trp operon attenuation in which the elevated basal level readthrough is determined by occasional ribosome release prior to synthesis of the 3:4 terminator hairpin.
 ...
PMID:Replacement of the Escherichia coli trp operon attenuation control codons alters operon expression. 223 31


1 2 3 4 5 6 7 8 9 10 Next >>