Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present communication a characterization of the 5 S rRNA genes and the tRNA genes of Tetrahymena pyriformis has been performed. The number of 5 S rRNA and tRNA genes in the macromolecular DNA has been established. Furthermore no sequence homology is observed for these genes. The number of both types of genes does not change significantly under starvation conditions. The genomic organization of the 5 S rRNA and tRNA genes has been investigated. From in vivo replication studies it is concluded, that replication of both 5 S rRNA and tRNA genes takes place throughout the whole S-period.
 ...
PMID:The genes for 5 S ribosomal RNA and transfer RNA in Tetrahymena pyriformis. 41 50

Changes in the translational machinery components of the Bombyx mori posterior silk gland were analysed during starvation and refeeding and compared to the regularly fed larvae. During starvation, tRNA and ribosomal RNA synthesis are stopped. The amounts of different RNA classes and of the different tRNA species slow down at the same rate. Thus various tRNA show similar half-lifes and the preexisting tRNA adaptation to fibroin mRNA translation persists during starvation. Similarly, the tRNA/rRNA ratio is constant during starvation and refeeding (12 tRNA molecules for one ribosome) as in silk glands of control animals. Aminoacyl-tRNA synthetases and tRNA charging levels are decreased during starvation. The maximal tRNA charging level obtained during maximal protein synthesis in control animals is regained after 24 h refeeding of starved larvae. Changes observed in the free amino acid pool are not similar from one amino acid to another and levels reached after starvation do not differ strongly from the controls. Our results suggest that the production of translation apparatus components is coordinated and adjusted to the protein synthesis activity. Whether this coordination occurs in the silk gland is discussed on the basis of the "metabolic regulation", primarily described in prokaryotes and Yeast. Transfer RNA charging levels seem to play a key role in the process of regulation and could be implicated in the mechanism of tRNA adaptation if this phenomenon results as expected from a transcriptional control.
 ...
PMID:Effect of starvation on tRNA synthesis, amino acid pool, tRNA charging levels and aminoacyl-tRNA synthetase activities in the posterior silk gland of Bombyx mori L. 46 73

Psoas muscle of rats starved for 2 or 4 days contained increased levels of ribosomal subunits and exhibited reduced rates of protein synthesis in vitro, demonstrating a starvation-induced inhibition of peptide-chain initiation. The activity of an eIF-2-like initiation factor, assayed in postribosomal supernatants, decreased in psoas during starvation, parallel to a 25% reduction in the RNA level. Reduced eIF-2 activity did not result from nucleotide depletion or increased deacylation of initiator tRNA, nor was it abolished by extensive dialysis. Perfusion of psoas muscle in the presence of insulin reversed the starvation-induced block in peptide-chain initiation, but did not alter the activity of eIF-2 or level of RNA. Furthermore, heart muscle did not manifest a starvation-induced block in peptide-chain initiation even though the activity of eIF-2 and the level of RNA decreased as a result of food deprivation. Thus loss of eIF 2 activity in psoas and heart did not parallel changes in peptide-chain initiation but was associated with a reduction in tissue RNA. These results indicate that the level of eIF-2 is not rate-limiting for peptide-chain initiation under the conditions tested in this study.
 ...
PMID:Effect of starvation on initiation of protein synthesis in skeletal muscle and heart. 68 62

Inhibition of protein synthesis in relaxed control E. coli results in the formation of chromatographically unique isoacceptor species of phenylalanine tRNA. The genetic origin and some functional properties of the major unique species of tRNA (Phe) produced during leucine starvation were investigated. RNA:DNA hybridization analyses revealed that the normally occurring and major unique species of tRNA (Phe) are generated from DNA sequences which are identical or closely related and that there may be only one such sequence in the E. coli chromosome. Results from 32P pulse-chase experiments revealed that the unique tRNA (Phe) can be converted to a chromatographically normal form upon resumption of cell growth in fully supplemented medium. These findings, taken with earlier results which indicate that the unique species is not derived from preexisting, normally occurring species, indicate that the unique tRNA(Phe) is a modification-deficient form of the normal species. Comparative studies of the unique and normal phenylalanine tRNAs revealed that the unique species is aminoacylated at a much lower rate than the normal species and is only about 60% as efficient in a tRNA-dependent, poly(U)-directed protein synthesizing system.
 ...
PMID:Unique phenylalanine transfer ribonucleic acids in relaxed control Escherichia coli: genetic origin and some functional properties. 77 26

We suggest that two events are necessary for an asynchronous population of cells to undergo arrest in the GI phase of the cell cycle upon nutrient starvation. First, passage through GI must be prevented by a deficiency of some metabolic intermediate. Since this intermediate may act indirectly to arrest division, we designate it the "signal". We have found three conditions under which Saccharomyces cerevisiae cells arrest division in GI: sulfate starvation of a prototroph, methionine starvation of an auxotroph, or a shift of a conditional methionyl-tRNA synthetase mutant [L-methionine: tRNA Met ligase (AMP-forming), EC 6.1.1.10] to a restrictive condition. We interpret these results to indicate that the signal for sulfate starvation in S. cerevisiae is generated near the end of the sulfate assimilation pathway (at or beyond the formation of mehtionyl-tRNA). As a unifying hypothesis, we propose that the signal for all nutrients is generated at the level of protein biosynthesis.
 ...
PMID:Control of cell division in Saccharomyces cerevisiae by methionyl-tRNA. 77 94

Sulfur-deficient tRNA, isolated from Escherichia coli HfrC, rel-, met-, cys-, lambda, after cysteine starvation, was found to have an increased acceptance of isoleucine in proportion to the deficiency of 4-thiouridine. Isoleucine acceptance was not altered in the presence of other amino acids of CTP, and the higher acceptance was observed over a wide range of magnesium, isoleucine, tRNA and enzyme concentrations. The Vmax value for sulfur-deficient tRNA was more than three times greater than observed for normal tRNA. Methylated albumin kieselguhr (MAK) chromatography revealed three isoacceptor peak for normal tRNA, while sulfur-deficient tRNA was missing tRNAile, and exhibited a larger, shifted peaks for tRNA normal tRNA, while sulfur-deficient tRNA was missing tRNAille 2, and exhibited a large shifted peak for tRNAile 3 . Treatment with crude RNA sulfurtransferase both lowered the isoleucine acceptance for sulfur-deficient tRNA to that seen for normal tRNA, and restored the missing isoacceptor on MAK. The possibility that thionucleotides may play a role in the aminoacylation of tRNAile in E. coli is discussed.
 ...
PMID:Increased isoleucine acceptance by sulfur-deficient transfer RNA from Escherichia coli. 78 31

The heterogeneity of undermodified phenylalanine tRNA produced in relaxed control E. coli during amino acid starvation was investigated. Examination of the RPC-5 elution profiles of tRNAPhe prepared from non-starved cells and cells starved of a variety of amino acids, including some known to be involved in the formation of modified bases revealed that: (1) only one species of fully modified tRNAPhe appears to occur in cells grown in enriched medium; (2) at least two chromatographically unique isoacceptor species are observed in addition to the normal tRNAPhe in starved cells; (3) the unique, undermodified species of tRNAPhe from leucine-starved cells, known to be deficient in dihydrouridine, pseudouridine, 2-thiomethyl-N6-(delta2-isopentenyl) adenosine and 3-(3-amino-3-carboxypropyl) uridine, co-elute with the unique species produced in cells starved of histidine or arginine or treated with puromycin or chloramphenicol; (4) additional unique species of tRNAPhe can be detected in methyl- and sulfur-deficient tRNA from methionine- and cysteine-starved cells; (5) analysis of phenoxyacetylated tRNA revealed that the chromatographically unique and normal species from starved cells contain subspecies deficient in 3-(3-amino-3-carboxypropyl) uridine; and (6) using phenoxyacetylation as a means of effecting the resolution of undermodified subspecies, a total of at least ten chromatographically unique subspecies of rRNAPhe were detected in an organism that appears to posses only one gene for tRNAPhe. Taken together, the results support the view that there are both general and specific effects of amino acid starvation on the post-transcriptional modification of tRNA.
 ...
PMID:General and specific effects of amino acid starvation on the formation of undermodified Escherichia coli phenylalanine tRNA. 79 74

Bacillus subtilis cells accumulate unusual phosphorylated substances at the end of logarithmic growth in a semi-synthetic medium. Two of these substances are guanosine 3'(2')-diphosphate 5'-diphosphate (ppGpp) and guanosine 3'(2')-diphosphate 5'-triohosphate (pppGpp) which, in contrast to amino-acid-starved Escherichia coli cells, are not degraded in sporulating cells of B. subtilis after the addition of chloramphenicol. Moreover, inhibition of protein synthesis in growing cells of B. subtilis causes accumulation of ppGpp and pppGpp, which is also in contrast to E. coli. This was shown by isolation and characterization of substances produced in these cells after the addition of chloramphenicol. Other inhibitors of protein synthesis acting at the ribosomal level also cause the accumulation of ppGpp and pppGpp. There is no difference between the action of antibiotics affecting 50-S and/or 30-S ribosomal subunits, since chloramphenicol, tetracycline erythromycin and neomycin cause the accumulation of almost equal amounts of these nucleotides. This apparently resolves the close connection between ppGpp accumulation and the rate of stable RNA synthesis, which was believed to exist also in B. subtilis because of the stringent response observed after amino acid starvation coupled with ppGpp accumulation. Antibiotics which inhibit protein synthesis differently than by affecting the ribosomes (puromycin) or which inhibit RNA (rifampicin) or DNA (nalidixic acid) synthesis do not cause ppGpp accumulation. The accumulation of ppGpp and pppGpp in the presence of charged tRNA provided by chloramphenicol treatment suggests that the signal for the synthesis of unusual nucleotides is an inhibition of the binding of tRNA (charged or uncharged) to the acceptor site of the ribosome. This activates the rel gene product which forms ppGpp and pppGpp from GTP and ATP. Sporulating cells of B. subtilis without chloramphenicol treatment produce besides ppGpp and pppGpp other unusual substances, which are likely to be highly phosphorylated nucleotides contained adenine as base moiety.
 ...
PMID:Studies on the control of development. Accumulation of guanosine tetraphosphate and pentaphosphate in response to inhibition of protein synthesis in Bacillus subtilis. 80 77

tRNA synthesis in the early loach embryos of different ploidy and factors of the activation of synthesis and the maturation of tRNA molecules at the mid-blastula stage have been studied. tRNA synthesis is activated at the early- and mid-blastula and in the beginning of gastrulation. The normal activation of synthesis and maturation of tRNA molecules require the embryo to be maintained in the contact with the yolk at the earlier developmental stages. The methionine starvation may be one of the factors limiting the rate of tRNA maturation. The activity of tRNA synthesis during blastulation was shown to depend on gene dosage. At this stage the paternal and maternal tRNA genes are transcribed independently. In the beginning of gastrulation, the type of tRNA synthesis control markedly changes and the effect of gene dose compensation manifests itself, that is typical for the control of rRNA synthesis as well. The data obtained are discussed with respect to the state of protein synthesizing system at the moment of activation of specific protein syntheses with the onset of morphogenesis.
 ...
PMID:[Transport RNA in early embryogenesis of fish. 3. Certain problems of regulation of RNA synthesis at the early stages of development of the loach (Misgurnus fossilis (1)]. 93 85

A study of in vivo and in vitro methylation of tRNAs in regulatory mutants affected in methionine-mediated repression (eth2, eth3, eth10) has led to the following results: 1) The eth2-2 carrying strain presents a great undermethylation of its tRNAs of the same order of magnitude as observed during methionine starvation of methionine auxotrophs. 2) This undermethylation leads to a shift of the tRNAIII met peak on a BD cellulose column, while tRNAIII met peak is unchanged. 3) The study of a double mutant strain carrying eth2 and met2 mutations has shown that this undermethylation is a consequence of the high internal pool of methionine. 4) Undermethylation unequally affects the different bases and the different tRNA species.
 ...
PMID:tRNAs undermethylation in a met-regulatory mutant of Saccharomyces cerevisiae. 109 67


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