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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A starvation-inducible DNA-binding protein was discovered as a result of the analysis of proteins synthesized in 3-day-old cultures of Escherichia coli. This 19-kD protein, designated Dps, is abundant in starved cells. In vitro, Dps forms extremely stable complexes with DNA, without apparent sequence specificity. When complexed with Dps, DNA is rendered DNase resistant. Mutant cells lacking Dps show dramatic changes in the pattern of proteins synthesized during starvation. The mutants also fail to develop starvation-induced resistance to hydrogen peroxide, an agent that can cause oxidative damage to DNA in vivo. These results have prompted us to postulate that Dps plays an important role both in gene expression and DNA protection during stationary phase. The existence of similar proteins, heretofore with no known function, in bacterial species distantly related to Escherichia coli suggests that Dps may define a novel class of widely conserved DNA-binding proteins.
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PMID:A novel DNA-binding protein with regulatory and protective roles in starved Escherichia coli. 134 Apr 75

Bacteriophage Mud (Casadaban and Cohen 1979) was used to bring the transcription of the gene for beta galactosidase (lacZ) under the control of the promoter of the structural gene for colicin Ib (cia(Ib)) on a derivative of the Col plasmid Col-Ib.P9. Transcription of this fusion operon was stimulated by agents which damaged cellular DNA (mitomycin C, bleomycin and colicin E2). Increased transcription of the cia-lacZ operon could be detected within 13 min of the addition of these agents. In a strain bearing the tif-1 (recA441) mutation, constitutive expression of the SOS DNA repair system at 42 degree C also increased transcription of the cia-lacZ operon. Transcription of the cia-lacZ operon was also stimulated by inhibition of DNA gyrase activity with nalidixic acid but not with novobiocin. Transitory inhibition of protein synthesis with chloramphenicol or by proline starvation of a proline auxotroph did not stimulate cia-lacZ transcription. Transcription of the cia-lacZ operon was substantially reduced in the presence of a recA mutation, but was largely unaffected by a mutation in recB affecting the RecBC DNase or by catabolite repression. Control experiments in which the production of colicin Ib was measured confirmed that the experiments with the fusion operon gave an accurate indication as to the activity of the wild type cia gene except for the effect of catabolite repression, where we observed up to 99% reduction in colicin Ib production in strains carrying mutant crp or cya alleles. The overall results confirm previous suggestions that there was considerable similarity between the regulatory systems controlling production of colicins and the repressor-dependent regulation of lambdoid prophage induction.
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PMID:Transcription regulation of colicin Ib synthesis. 646 Sep 13

Cultured human glial cells were blocked in interphase (G1) by 24 h of serum starvation and subsequently subjected to 200 Gy, 8 MV X-radiation. Immediately following irradiation the cultures were transferred to serum-containig medium. Time-lapse cinemicrography performed during the next 48 h showed a profoundly disturbed motility with decreased ability for polarization and locomotion of the irradiated cells. Specimens fixed 24 and 48 h after irradiation and investigated by immunofluorescence with tubulin-antibodies and DNase/DNase-antibodies, and by whole cell transmission electron microscopy showed derangements in the distribution of microfilament bundles related to the cytoplasmic ramification of the irradiated cells, but otherwise no detectable alterations in structure or distribution of either microtubules or microfilaments. It is suggested that the alteration in the arrangement of filament bundles is of importance to the impaired locomotion of the irradiated cells.
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PMID:Cytoplasmic effects of X-irradiation on cultured cells in a non-dividing stage. 4. Studies of sparsely grown, serum-deprived cells. 700 75

In plasmodia of Physarum polycephalum, DNase activity with a preference for native DNA was found in a pattern of three or four isoenzymes. During growth a constant specific activity of approx. 0.3 unit of DNase activity per mg protein was found in the plasmodia, with a broad maximum during the G2-phase in the naturally synchronous flat cultures. Under conditions of starvation or sclerotization, DNase activity was secreted by the plasmodia in amounts which were up to ten times higher than the internal level of enzyme activity. Purification of the secreted DNase activity to high purity by three simple chromatographic steps showed that four different DNase isoenzymes existed which were identical with the intracellular ones. The relative abundances of the various isoenzyme forms inside and outside the plasmodia seemed to be slightly different. The possible functions of the DNase activities are discussed.
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PMID:Nucleic acids and related enzymes. Secretion of four alkaline DNases by plasmodia of Physarum polycephalum. 746 1

High-carbohydrate feeding and triiodothyronine (T3) increase the abundance of acetyl-CoA carboxylase-alpha (ACC alpha) mRNA in avian hepatocytes, whereas starvation, glucagon, and medium-chain fatty acids decrease the abundance of ACC alpha mRNA. These changes in ACC alpha mRNA levels are mediated by alterations in the rate of transcription of the ACC alpha gene. In liver, ACC alpha transcription is initiated from two promoters, promoter 1 and promoter 2, resulting in transcripts that contain heterogeneity in their 5'-untranslated regions. Here, we investigated the role of promoter 1 and promoter 2 in mediating nutrient- and hormone-induced changes in ACC alpha mRNA abundance by measuring the level of transcripts expressed from promoter 1 and promoter 2 using a ribonuclease protection assay. The results indicated that both promoter 1 and promoter 2 were regulated by starvation/refeeding in livers of intact chicks and by T3, glucagon, and medium-chain fatty acids in chick embryo hepatocyte cultures and that alterations in the activity of promoter 2 accounted for a greater proportion of the changes in total ACC alpha mRNA abundance caused by nutrient and hormone treatment. Five DNase-hypersensitive sites were also identified between -500 and +1 bp relative to the transcription start site of promoter 2 in livers of intact chicks and in chick embryo hepatocyte cultures. In transient transfection analyses, this region of DNase hypersensitivity conferred regulation of transcription by T3, glucagon, and medium-chain fatty acids in chick embryo hepatocytes. Data from this study demonstrate that diet-induced changes in the activities of promoter 1 and promoter 2 in livers of intact chicks are mimicked in chick embryo hepatocyte cultures by manipulating the concentrations of T3, glucagon and medium-chain fatty acids in the culture medium and that cis-acting sequences mediating the effects of nutrients and hormones on promoter 2 activity are located immediately upstream of the transcription start site of this promoter.
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PMID:Thyroid hormone, glucagon, and medium-chain fatty acids regulate transcription initiated from promoter 1 and promoter 2 of the acetyl-CoA carboxylase-alpha gene in chick embryo hepatocytes. 1111 20

The mitotic phases and the changes that the chromatin and mitotic microtubules undergo during mitosis in the sexually transmitted parasite Trichomonas vaginalis are described. Parasites arrested in the gap 2 phase of the cell cycle by nutrient starvation were induced to mitosis by addition of fresh whole medium. [(3)H] Thymidine labeling of trichomonad parasites for 24 h showed that parasites have at least four synchronic duplications after mitosis induction. Fixed or live and acridine orange (AO)-stained trichomonads analyzed at different times during mitosis by epifluorescence microscopy showed that mitosis took about 45 min and is divided into five stages: prophase, metaphase, early and late anaphase, early and late telophase, and cytokinesis. The AO-stained nucleus of live trichomonads showed green (DNA) and orange (RNA) fluorescence, and the nucleic acid nature was confirmed by DNase and RNase treatment, respectively. The chromatin appeared partially condensed during interphase. At metaphase, it appeared as six condensed chromosomes, as recently reported, which decondensed at anaphase and migrated to the nuclear poles at telophase. In addition, small bundles of microtubules (as hemispindles) were detected only in metaphase with the polyclonal antibody anti-Entamoeba histolytica alpha-tubulin. This antibody showed that the hemispindle and an atractophore-like structure seem to duplicate and polarize during metaphase. In conclusion, T. vaginalis mitosis involves five mitotic phases in which the chromatin undergoes different degrees of condensation, from chromosomes to decondensed chromatin, and two hemispindles that are observed only in the metaphase stage.
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PMID:Trichomonas vaginalis: chromatin and mitotic spindle during mitosis. 1116 63

DNase gamma, which cleaves chromosomal DNA into nucleosomal units (DNA ladder formation), has been suggested to be the critical component of apoptotic machinery. Using rat pheochromocytoma PC12 cells, which are differentiated to sympathetic neurons by nerve growth factor (NGF), we investigated whether DNase gamma-like enzyme is present in neuronal cells and is involved in neuronal cell death. The nuclear auto-digestion assay for DNase catalyzing internucleosomal DNA cleavage revealed that nuclei from neuronal differentiated PC12 cells contain acidic and neutral endonucleases, while nuclei from undifferentiated PC12 cells have only acidic endonuclease. The DNA ladder formation observed in isolated nuclei from neuronal differentiated PC12 cells at neutral pH requires both Ca(2+) and Mg(2+), and is sensitive to Zn(2+). The molecular mass of the neutral endonuclease present in neuronal differentiated PC12 cell nuclei is 32000 as determined by activity gel analysis (zymography). The properties of the neuronal endonuclease present in neuronal differentiated PC12 cell nuclei were similar to those of purified DNase gamma from rat thymocytes and splenocytes. Interestingly, in neuronal differentiated PC12 cells, internucleosomal DNA fragmentation is observed following NGF deprivation, whereas undifferentiated PC12 cells fail to exhibit DNA ladder formation during cell death by serum starvation. These results suggest that the DNase gamma-like endonuclease present in neuronal differentiated PC12 cell nuclei is involved in internucleosomal DNA fragmentation during apoptosis, induced by NGF deprivation.
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PMID:Presence of DNase gamma-like endonuclease in nuclei of neuronal differentiated PC12 cells. 1464 7

The effect of long-term phosphate (Pi) starvation of up to 3 weeks on the levels of purine nucleotides and related compounds was examined using suspension-cultured Catharanthus roseus cells. Levels of adenine and guanine nucleotides, especially ATP and GTP, were markedly reduced during Pi-starvation. There was an increase in the activity of RNase, DNase, 5'- and 3'-nucleotidases and acid phosphatase, which may participate in the hydrolysis of nucleic acids and nucleotides. Accumulation of adenosine, adenine, guanosine and guanine was observed during the long-term Pi starvation. Long-term Pi starvation markedly depressed the flux of transport of exogenously supplied [8-(14)C]adenosine and [8-(14)C]adenine, but these labelled compounds which were taken up by the cells were readily converted to adenine nucleotides even in Pi-starved cells, in which RNA synthesis from these precursors was significantly reduced. The activities of adenosine kinase, adenine phosphoribosyltransferase and adenosine nucleosidase were maintained at a high level in long-term Pi starved cells.
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PMID:Effect of long-term phosphate starvation on the levels and metabolism of purine nucleotides in suspension-cultured Catharanthus roseus cells. 1632 9

HOX homeobox proteins are key oncogenic drivers in hematopoietic malignancies. Here we demonstrate that HOXA1, HOXA6 and predominantly HOXA9 are able to induce the production of insulin-like growth factor 1 (Igf1). In chromatin immunoprecipitations, HOXA9 bound directly to the putative promoter and a DNase-hypersensitive region in the first intron of the Igf1 gene. Transcription rates of the Igf1 gene paralleled HOXA9 activity. Primary cells transformed by HOXA9 expressed functional Igf1 receptors and activated the protein kinase Akt in response to Igf1 stimulation, suggesting the existence of an autocrine signaling loop. Genomic deletion of the Igf1 gene by Cre-mediated recombination increased sensitivity toward apoptosis after serum starvation. In addition, the leukemogenic potential of Igf1-negative, HOXA9-transformed cells was impaired, leading to a significant delay in disease development on transplantation into recipient animals.
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PMID:Insulin-like growth factor 1 is a direct HOXA9 target important for hematopoietic transformation. 2525 70

Deoxyribonucleases (DNases) play a major role in apoptotic DNA fragmentation/degradation, and apoptotic-like DNA degradation is also observed during conjugation of the ciliate Tetrahymena thermophila; however, the characteristics of neutral and acidic DNases are still undefined in its life stages. Here, we report the biochemical characterization of DNase activities displayed in three different Tetrahymena life stages in a comparative manner. Maximum DNase activity of Tetrahymena was observed under acidic conditions, indicating that Tetrahymena has strong DNase II-like activities. Zymography revealed that Tetrahymena has at least five distinct DNase activity bands at 28, 32, 33.8, 35.5, and 69-kDa, and that the activities at 32 and 33.8-kDa were also secreted into starvation buffer. Cofactor analysis demonstrated that Mg(2+) exerted inhibitory effects on neutral DNase activities. Unexpectedly, Mg(2+) and Ca(2+) had favorable effects on acidic DNase activities. The DNase activity profile of conjugating Tetrahymena cells revealed that the 32 and 33.8-kDa activities at pH 5.0 increased from 14 to 18 h of conjugation, corresponding to the final resorption of the old macronucleus by lysosomal enzymes during programmed nuclear death (PND). Overall, we found that Tetrahymena DNases exhibit different biochemical properties and a possible involvement of DNase II-like activities in PND.
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PMID:Identification of neutral and acidic deoxyribonuclease activities in Tetrahymena thermophila life stages. 2585 43


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