Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two plasmids that overproduce the colicin A lysis proteins, Cal, are described. Plasmid AT1 was constructed by a deletion in the colicin A operon, which placed the cal gene near a truncated caa gene in such a way that both gene products wer synthesized at high levels following induction. Plasmid CK4 was constructed by insertion of the cal gene downstream from the tac promoter of an expression vector. Overproduction of Cal was obtained after mitomycin C induction of pAT1 cells and after IPTG induction of pCK4 cells. The kinetics of Cal synthesis were examined with [35S] methionine and [2-3H] glycerol in lpp or lpp+ host strains. Each of the steps of the lipid modification and maturation pathway of Cal was demonstrated. The modified precursor form of overproduced Cal was not chased as efficiently as when it is produced in pColA cells. After treatment with globomycin, a significant amount of this modified precursor form accumulated and was degraded with time into smaller acylated proteins, but without release of the signal peptide. Release of cellular proteins and quasi-lysis were observed after about 1 hour of induction for cells containing either plasmid. In addition, in Cal-overproducing cells, the rate of quasi-lysis was increased but not its extent. In pldA cells, quasi-lysis was reduced but not abolished. Lethality of the Cal induction in the overproducing cells was in th same range as that in wild-type cells.
 ...
PMID:High-level expression of the colicin A lysis protein. 250 57

In order to investigate the biochemical events involved in potentially lethal DNA damage repair (PLDR), we have identified a pleiotropic protein expression response that is activated upon X-irradiation of confluence-arrested human malignant melanoma (U1-Mel) cells. Plateau-phase U1-Mel cells were selected because of their extraordinary capacity for PLDR. Eight major X-ray-induced polypeptides (XIPs) of Mr 126,000-275,000 (i.e., XIP126 through XIP275) were detected by resolving L-[35S]methionine-labeled whole cell extracts using two-dimensional gel electrophoresis. XIPs were found in unirradiated, proliferating U1-Mel cells, shut off under plateau-phase conditions and resynthesized in response to X-irradiation. The expression of three classes of proteins was affected by X-irradiation. Class I proteins, XIP145 and XIP269, were induced linearly with increasing X-ray doses. The rate of synthesis of class II proteins, XIP126, XIP135, XIP138, XIP141, XIP147, and XIP275, increased linearly with low X-irradiation doses, but plateaued at doses of 150-250 cGy. In contrast, the expression of class III proteins, 47,000 and 254,000 Mr proteins, decreased with increasing X-ray doses. Tumor, cancer-prone, and normal human cells, which represent a wide range of cells with varied repair capacities, were investigated to better understand the role of XIPs in DNA damage responses. X-irradiated normal and tumor cells induced the synthesis of XIP145 and XIP269. A strong correlation between the induction of XIP269 and PLDR capacity, as measured by delayed plating of plateau-phase cells, was noted. XIP269 was present in six of seven normal and tumor cells types, but was completely absent in cells from patients with Bloom's syndrome and ataxia telangiectasia. X-irradiated Fanconi's anemia and xeroderma pigmentosum cells synthesized low levels of XIP269. The majority of XIPs synthesized by X-irradiated cells from cancer-prone patients were of low molecular weights. A number of XIP expression characteristics suggest their role in either gross chromosomal PLDR and/or in X-ray adaptivity responses: (a) XIP expression was inhibited by 1 microgram/ml cycloheximide, a dose which decreased survival 6-fold during PLDR holding and resulted in greater than 80% inhibition of protein synthesis; (b) XIP expression was specific for ionizing radiation damage, since heat shock, hypoxia, and alkylating agents failed to induce their synthesis; (c) the time course of expression was long, with the first appearance of XIPs at 3 h and maximal expression at 4 h.
 ...
PMID:Identification and characterization of X-ray-induced proteins in human cells. 272 Jun 48

In attempts to transform and immortalize human cell cultures, skin fibroblasts from normal donors of different ages, from patients with the premature ageing diseases Werner's syndrome (WS) and progeria (PR), and from donors with the cancer-prone diseases ataxia telangiectasia (AT), Bloom's syndrome (BS) and Fanconi's anaemia (FA), were infected with SV40 virus and their growth monitored thereafter. Lesch-Nyhan (LN) fibroblasts were also infected. SV40-infected cultures from two normal and from WS, AT and LN donors attained a spectrum of transformed properties, high mitotic activity at confluence, presence of T-antigen, anchorage independence and altered morphology. Most of these pretransformed cultures died in the crisis period. However, two cultures from the WS and LN patients survived the crisis period and have now been grown to more than 200 passages. For the LN culture the crisis period was at least 200 days. Both permanent lines retain the properties of pretransformed cells, but differ in their modal chromosome number and ability to grow in methionine-free medium. It can be concluded from these experiments that transformation by SV40 to permanent lines is a rare event in human skin fibroblasts, even when these cells were taken from patients predisposed to form cancers.
 ...
PMID:The susceptibility of Werner's syndrome and other human skin fibroblasts to SV40-induced transformation and immortalization. 287 33

Cell lines established from donors with the inherited disorder ataxia-telangiectasia (A-T) exhibit exceptional sensitivity to ionizing radiation and chemicals known to produce increased levels of intracellular H2O2, suggesting a deficiency in glutathione-dependent detoxication reactions. Glutathione (GSH) biosynthesis in fibroblast and lymphoblast cultures derived from individuals known to be clinically unaffected, homozygous, or heterozygous for A-T was assessed. Following GSH depletion by diethylmaleate, fibroblasts (GM 3492) from a clinically unaffected individual resynthesized GSH at a rate approximately twice that observed in fibroblasts from known heterozygotes (GM 3488 and GM 3489). Unrelated A-T homozygote fibroblast lines GM 3487B and GM 5823 resynthesized GSH only very slowly. GM 3492 cells repleted intracellular GSH by 6 h after depletion, the heterozygote lines by 18 h. The A-T homozygotes replaced only 30% of the intracellular GSH pool by 24 h. A lymphoblast cell line from the A-T homozygote (GM 3189) also exhibited slow resynthesis after depletion. However, if these cells were permeabilized by treatment with digitonin, GSH synthesis proceeded at a rate exceeding synthesis in permeabilized or untreated normal lymphoblasts (GM 3323). The first enzyme in GSH synthesis, gamma-glutamylcysteine synthetase, was found to be elevated about 2.7-fold in A-T homozygote fibroblasts, suggesting that a substrate for GSH synthesis may be rate limiting. A-T homozygote lymphoblasts contained about 2-fold more gamma-cystathionase activity over other cell lines tested suggesting increased flux through the transsulfuration pathway for cysteine production in response to reduced cysteine supply. Transport of cysteine and cystine was found to be 8- and 5-fold slower in A-T homozygotes that did not affect fibroblasts while glutamate and methionine transport Vmax did not differ among the cell lines tested. These experiments demonstrate that cells from A-T homozygotes are deficient in cysteine transport, thus limiting GSH resynthesis after a depleting challenge such as radiation or GSH-depleting xenobiotic compounds.
 ...
PMID:Imparied glutathione biosynthesis in cultured human ataxia-telangiectasia cells. 362 Nov 55

Several experimental studies point to a potential role of angiotensin II (Ang II) in the progression of glomerulosclerosis even in the absence of glomerular hypertension. We tested the hypothesis that Ang II acts as a growth factor for adult human mesangial cells (AHMC). AHMC were isolated from noninvolved parts of tumor nephrectomy specimens and grown in RPMI medium with the addition of fetal calf serum (FCS). All studies were performed with growth-arrested cells. Proliferation studies were done in serum-free standard growth medium (SF) with the addition of either various concentrations of insulin, plasma-derived serum, or FCS. Ang II (10(-10) to 10(-6) M) dose dependently increased the 3H-thymidine uptake of AHMC up to 57 +/- 13% over solvent controls (p < 0.01). In parallel, the DNA content was 36 +/- 10% higher (p < 0.05) than in solvent controls after 2 days of culture. The cell numbers were higher up to 47 +/- 8% in Ang II (10(-6) M) stimulated cultures after 4 days of incubation (p < 0.01). The effect of Ang II was specific, since it was almost completely obliterated by the AT1 receptor antagonist DuP753. The effect of Ang II was particularly marked when cultures were incubated with SF plus high concentrations (1.7 x 10(-6) M) of insulin or SF plus 10% plasma-derived serum. In contrast, the effect was not significant when cultures were incubated with SF plus 10% FCS. Ang II, when added to platelet-derived growth factor at various concentrations, did not further increase the proliferation. The effect on protein synthesis was assessed in growth-arrested AHMC by 3H-methionine uptake and protein/DNA ratio in cell lysates. Ang II (10(-10) to 10(-6) M) dose dependently increased the 3H-methionine uptake of AHMC up to 47 +/- 10% over solvent controls (p < 0.01). In parallel Ang II (10(-8) to 10(-6) M) dose dependently increased the 3H-methionine uptake of the protein/DNA ratio by 24 +/- 6% after 48 h of incubation. DuP753 obliterated the stimulatory effect of Ang II. Ang II (10(-6) M) also increased the mRNA of the immediate-early growth-related gene Egr-1. We conclude that Ang II induces hypertrophy and proliferation in adult human mesangial cells. This result is of interest with respect to a potential role of Ang II in the pathogenesis of glomerulosclerosis in humans.
 ...
PMID:Angiotensin II induces hypertrophy and hyperplasia in adult human mesangial cells. 771 40

We have isolated from a genomic library using PCR amplification an 1171 base sequence containing a putative ovine AT1-R protein coding sequence of 1080 bases. As expected the protein coding sequence is of greater than 99% homology to the partial protein coding sequence reported by Robillard et al, with only one base difference. Relative to other species, highest homology at the level of the cDNA protein coding sequence is to bovine (97.6%) and lowest homology to rat Type 1a (83.3%). The predicted protein amino acid sequence in turn encodes a protein with the properties of a seven alpha-helix transmembrane receptor (by TMPred) sharing closest homology (98.6%) to the bovine receptor and lowest to the rat Type 1a (90.2%). As expected from such a high degree of interspecies homology, amino acids identified by site-directed mutagenesis of the human or rat AT1A-R as involved in binding and action of AII are very highly conserved in the ovine sequence. In addition, both bovine and ovine AT1-R are known to exhibit lower affinity for DuP753 than human AT1-R, and in bovine AT1-R this has been suggested to coincide with the amino acid substitutions Ala->Thr (163) and Leu->Met (262) relative to the human sequence. Our ovine AT1-R cDNA sequence shares these same bovine substitutions.
 ...
PMID:Isolation of an ovine genomic sequence containing the full-length angiotensin II type-1 receptor. 988 11

Angiotensin II (AII) analogs bearing n-Leu, Met or S-substituted groups for cysteine at position 5 were studied regarding their agonistic and tachyphylactic properties. It was shown that these analogs lowered the relative affinity towards the AT1 receptor as determined by contractile responses, which could be due to the removal of the beta-branching residue at position 5. Insertion of a sulfur atom in a different position away from the attached backbone carbon atom presented no significant difference in EC50 values for these analogs. Interestingly, the S-bearing analogs at position 5 were full agonists but the tachyphylactic property was lost, in contrast to [n-Leu5]AII, which still induced reduction of the contractile responses. Nevertheless after replacing the Asp with Sar in position 1 (Sar1) tachyphylaxis was again established. It is concluded that the insertion of Met or an S-substituted cysteine into the side chain at position 5 of AII may promote interactions with its receptor due to the slight electronegative character of the sulfur atom and changes in the restricted conformational freedom of the Ile5 residue in the AII molecule. This was overcome by Sar1, probably through interactions due to its fully protonated N-terminal amino group and favoring the conformation responsible for the tachyphylaxis phenomenon.
 ...
PMID:Insertion of an electronegative sulfur atom in the side chain of position 5 of angiotensin II: changes in the tachyphylactic properties of the peptide. 1040 43

The ATDC gene was cloned using functional complementation and complements the radiosensitivity of ataxia telangiectasia (AT) group D cells. Although a number of transcripts have been detected, only a 3.0 kb cDNA found in a HeLa cell cDNA library has been cloned. Since AT group D cells express only a 2.4 kb transcript, efforts were made to clone and sequence this transcript. Using a biotinylated oligonucleotide probe, mRNA preparations were enriched in ATDC-related sequences. After this enrichment, 2.4 kb clones were obtained from the resulting library. The 2.4 kb transcript appears to be untranslated, since no protein from this transcript has been detected in AT group D cells, and this transcript is probably non-functional, since a splicing variation has positioned part of intron 1 near the first methionine codon in exon 1, eliminating most of exon 1 and important functional regions from this transcript. This transcript now has a stop codon located 33 bp in front of the first methionine, which would stop translation after the eleventh amino acid. As a result of these changes, the AT group D cell line (AT5BI) expresses no functional ATDC protein.
 ...
PMID:Altered splicing of the ATDC message in ataxia telangiectasia group D cells results in the absence of a functional protein. 1071 33

Four sets of angiotensin II (AngII) analogues with position 5 modifications, two agonist series with either Asp or Sar in position 1 and L-Phe in position 8, and two antagonist series with again Asp or Sar in position 1 and Leu in position 8 were synthesized. Modifications in positions 5 were introduced successively: Ile, Nle, Met, S-ethyl Cys, S-n-propyl-Cys, S-n-butyl Cys, S-t-butyl Cys and S-benzyl Cys in all four series. The study was undertaken in order to investigate the 5-position residue of AngII by replacing the hydrophobic side-chain by another containing an electrophilic moiety. The analogues were synthesised by solid phase synthesis using the Boc/Bzl or Fmoc/But strategy. All analogues were evaluated by their binding properties to the AT1 receptor on bovine adrenocortical membranes (bAT1). The results indicate that AngII analogues bind, irrespective of their agonistic or antagonistic nature or of their position 1 modification, in a similar manner and that position 5 modifications without beta-branching behave in an additive manner towards their affinity.
 ...
PMID:Angiotensin II analogues with sulphur-containing side-chains in position 5. A structure-activity relationship study. 1091 44

Probing G-protein coupled receptor (GPCR) structures is a priority in the functional and structural understanding of GPCRs. In the past, we have used several approaches around photoaffinity labeling in order to establish contact points between peptide ligands and their cognate receptors. Such contact points are helpful to build reality based molecular models of GPCRs and to elucidate their activation mechanisms. Most studies of peptidergic GPCRs have been done with photolabeling peptides containing the benzophenone moiety as a reputedly non-selective probe. However our recent results are now showing that p-benzoylphenylalanine (Bpa) has some selectivity for Met residues in the receptor protein, reducing the accuracy of this method. Turning a problem into an asset, modified analogues of Bpa, e.g. p,p'-nitrobenzoylphenylalanine (NO2Bpa), display increased selectivity for such Met residues. It means a photoprobe containing such modified benzophenone-moieties does not label a receptor protein unless a Met residue is in the immediate vicinity. This unique property allows us to propose and show the feasibility and utility of a new method for scanning the contact areas of peptidergic GPCRs, the Methionine Proximity Assay (MPA). Putative contact residues of the receptor are exchanged to Met residues by site-directed mutagenesis and are subjected to photoaffinity labeling with such modified benzophenone-containing peptides. Successful incorporation indicates physical proximity of those residues. This principle is established and explored with benzophenone-containing analogues of angiotensin II and the two known human angiotensin II receptors AT1 and AT2, determining contact points in both receptors. This approach has several important advantages over other scanning approaches, e.g., the SCAM procedure, since the MPA-method can be used in the hydrophobic core of receptors.
 ...
PMID:Methionine proximity assay, a novel method for exploring peptide ligand-receptor interaction. 1250 23


1 2 3 4 5 Next >>