Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the influence of the nucleotide sequence adjacent to the recognition site on the rate of cleavage of DNA by the restriction endonuclease EcoRI. For this purpose two decadeoxynucleotides, d(G-G-G-A-A-T-T-C-T-T) (Ia) and d(A-A-G-A-A-T-T-C-C-C) (Ib) were synthesized. The duplex Ia X Ib is cleaved by EcoRI preferentially in the dA-rich strand (approximately 10 times over the dG-rich strand). The individual nucleotides Ia and Ib are also cleaved by EcoRI, Ib at a higher rate than Ia and both at a lower rate than Ia X Ib. The temperature dependence of the reaction rate shows that only double-stranded oligodeoxynucleotides are substrates for the EcoRI endonuclease. We have, furthermore, synthesized oligomers of d(G-G-A-A-T-T-C-C), which contain two, three and four EcoRI sites, respectively. These oligodeoxynucleotides are preferentially cleaved at the sites next to the 5' end, where the recognition site is only flanked by one dG X dC base pair, in contrast to the other sites which are flanked by three such pairs. These data indicate that sequences adjacent to the recognition site influence the rate of cleavage: dA X dT base pairs enhance and dG X dC base pairs slow down the hydrolytic activity of the EcoRI endonuclease.
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PMID:The influence of sequences adjacent to the recognition site on the cleavage of oligodeoxynucleotides by the EcoRI endonuclease. 632 83

The optimal way of constructing a family of restriction endonuclease EcoRII substrates has been developed. The substrates are DNA-like duplexes containing regularly repeated native or modified sites of this enzyme as well as those of EcoRI and AluI. Synthesis of substrates was performed by water-soluble carbodiimide-induced polycondensation of two nonanucleotides, d(C-C-T-G-G-A-A-T-Tp) and d(C-C-A-G-G-A-G-C-Tp), as constituents of different complementary complexes. The products of reaction (degree of polymerization, 2-20) were isolated by G-200 gel-filtration. The yield of polymers was about 70%. The main products of reaction were dimers when dephosphorylated nonanucleotides (terminators of polycondensation) were used. The thermal stability of DNA-like duplexes is very high. The structure of the polymers obtained has been confirmed by UV-spectroscopy and by CD data as well as by the results of cleavage by EcoRI and AluI restriction endonucleases.
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PMID:[DNA-like duplexes containing repetitive sequences. VIII. Synthesis and properties of DNA fragments--substrates of restriction endonuclease EcoRII]. 632 67

The cellular basis for the enhanced sensitivity to ionising radiation and some DNA damaging chemicals in ataxia-telangiectasia (AT) cells is not clearly understood. Abnormalities in cell-cycle traverse, chromosome stability and DNA synthesis patterns have suggested that a chromatin associated defect may be the primary lesion in AT. This study involves an attempt to define such an anomaly by the use of a vital DNA specific bis-benzimidazole dye (Hoechst 33342) and deoxyribonuclease II as probes for chromatin organisation in intact and permeabilised human cells respectively. Despite similar DNA binding characteristics (determined by flow cytometry) of Ho33342 in normal and AT transformed fibroblasts, the AT cells show: (i) enhanced cell killing and increased accumulation of cells in G2 phase of the cell-cycle [both biological responses being relatively resistant in AT cells to modification by an inhibitor of poly (ADP ribosyl)ation], (ii) no resistance of de novo DNA synthesis to Ho33342-induced inhibition, (iii) elevated levels of slow-rejoining ligand-induced DNA strand-breaks, and (iv) enhanced expression of chromatin regions accessible to an exogenously supplied endonuclease. The results are interpreted on the basis that a chromatin anomaly of enhanced nuclease susceptibility, involving a minor fraction of the genome, may be a controlling factor in the expression of the various in vivo and in vitro characteristics of AT cells.
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PMID:Relationship between a chromatin anomaly in ataxia-telangiectasia cells and enhanced sensitivity to DNA damage. 648 55

An oligo(dT)-primed cDNA copy of the mRNA coding for the human gastrin precursor was constructed from poly(A)-containing RNA from a human pancreatic, gastrin-producing tumor (a gastrinoma). The cDNA was inserted into the Pst I endonuclease site of plasmid pBR322 by the use of the poly(dC) and poly(dG) tailing procedure. Clones containing gastrin sequences were selected by hybridization to a purified single-stranded 32P-labeled gastrin cDNA probe. This probe was constructed with gastrinoma mRNA as template. As primer for the cDNA synthesis, we used a synthetic oligonucleotide mixture, d(AG-A-A-AG-T-C-C-A-T-C-C-A), corresponding to the gastrin-specific amino acid sequence Trp-Met-Asp-Phe. In this way we determined the nucleotide sequence of the entire coding region (303 nucleotides), the entire 3' untranslated region (102 nucleotides), and 8 nucleotides of the 5' untranslated region. A striking homology between parts of the coding region suggests that evolution of the gastrin gene has involved a gene duplication.
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PMID:Molecular cloning of human gastrin cDNA: evidence for evolution of gastrin by gene duplication. 657 56

A study on the sequence dependent DNA binding mode of DAPI has been carried out on pUC8 and the beta gal promoter region by restriction endonuclease and DNAase I protection experiments. A molecular model depicting drug interaction at the level of selected palyndromes has also been constructed that confirms the A-T sequence specificity of the compound. Experimental data indicate that the binding sites for RNA polymerase and cyclic AMP receptor protein (CRP) in the beta gal gene are privileged locales for DAPI interaction, a feature that explains impairment of transcription at this level. From a stereochemical view point, DAPI binding to DNA minor groove, while being incompatible with promoter unwinding in the open complex, may also disturb optimal contacts with proteins regulating RNA polymerase activity.
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PMID:A model for the sequence-dependent DNA binding of 4',6-diamidino-2-phenylindole (DAPI). 788 47

Naturally occurring DNA variants of the single-cell-derived Y-02 stock of Trypanosoma cruzi were discovered during a routine assay of the stock. Three DNA variant types were isolated. One type was indistinguishable from the parental Y-02 stock on the basis of total DNA cell-1. The other two types contained approximately 30% and 70% more DNA cell-1 than the parental Y-02 stock. Both the nucleus and kinetoplast were involved in the DNA content differences. The increase in DNA cell-1 was not G-C- or A-T-specific and was unrelated to the developmental stage of the parasite. Epimastigote population doubling times, isoenzymes, and schizodeme analyses could not differentiate the variant stocks. However, marked karyotype polymorphisms were observed by pulse-field gel electrophoresis, and restriction-fragment-length-polymorphisms were detected in hybridizations of some endonuclease-restricted samples to the spliced leader probe. We postulate that the Y-02 variants are genetic homologs. The ability to form viable hybrids or aneuploids provides T. cruzi with a mechanism to survive environmental stress, promote intra-specific heterogeneity and generate the diversity observed in the presentation and course of Chagas' disease.
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PMID:Identification, isolation, and characterization of naturally-occurring Trypanosoma cruzi variants. 843 13

The effectiveness of cancer radiotherapy is compromised by the small proportion (approximately 5%) of patients who sustain severe normal tissue damage after standard radiotherapy treatments. Predictive tests are required to identify these highly radiosensitive cases. Patients with the rare, recessively inherited, cancer-prone syndrome ataxia-telangiectasia (A-T) sustain extremely severe normal tissue necrosis after radiotherapy and their cultured cells are also highly radiosensitive. Clinically normal carriers (heterozygotes) of the A-T gene have an increased risk of breast cancer, account for approximately 4% of all breast cancer cases and show a modest increase in cellular radiosensitivity in vitro. It has been suggested that a substantial proportion of highly radiosensitive (HR) breast cancer patients may be A-T heterozygotes, and that screening for mutations in the A-T gene could be used as a predictive test. We have tested this hypothesis in a group of cancer patients who showed adverse reactions to radiotherapy. Sixteen HR breast cancer patients showing mainly acute reactions (and seven HR patients with other cancers) were tested for ATM mutations using the restriction endonuclease fingerprinting assay. No mutations typical of those found in obligate A-T heterozygotes were detected. If the estimate that 4% of breast cancer cases are A-T gene carriers is correct, then ATM mutations do not confer clinical radiosensitivity. These early results suggest that screening for ATM mutations in cancer patients may not be of value in predicting adverse reactions.
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PMID:Absence of mutations in the ATM gene in breast cancer patients with severe responses to radiotherapy. 941 38

The ATM (A-T, mutated) gene on human chromosome 11q22.3 has recently been identified as the gene responsible for the human recessive disease ataxia-telangiectasia (A-T). In order to define the types of disease-causing ATM mutations in Japanese A-T patients as well as to look for possible mutational hotspots, reverse-transcribed RNA derived from ten patients belonging to eight unrelated Japanese A-T families was analyzed for mutations by the restriction endonuclease fingerprinting method. As has been reported by others, mutations that lead to exon skipping or premature protein truncation were also predominant in our mutants. Six different mutations were identified on 12 of the 16 alleles examined. Four were deletions involving a loss of a single exon: exon 7, exon 16, exon 33 or exon 35. The others were minute deletions, 4649delA in exon 33 and 7883del5 in exon 55. The mutations 4612del165 and 7883del5 were found in more than two unrelated families; 44% (7 of 16) of the mutant alleles had one of the two mutations. The 4612del165 mutations in three different families were all ascribed to the same T-->A substitution at the splice donor site in intron 33. Microsatellite genotyping around the ATM locus also indicated that a common haplotype was shared by the mutant alleles in both mutations. This suggests that these two founder mutations may be predominant among Japanese ATM mutant alleles.
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PMID:Mutations of the ATM gene detected in Japanese ataxia-telangiectasia patients: possible preponderance of the two founder mutations 4612del165 and 7883del5. 960 Feb 35

Germline mutations in the ATM gene are responsible for the autosomal recessive disorder ataxia-telangiectasia (A-T). In our study, we have determined the ATM mutation spectrum in 19 classical A-T patients, including some immigrant populations, as well as 12 of Dutch ethnic origin. Both the protein truncation test (PTT) and the restriction endonuclease fingerprinting (REF) method were used and compared for their detection efficiency, identifying 76% and 60% of the mutations, respectively. Most patients were found to be compound heterozygote. Seventeen mutations were distinct, of which 10 were not reported previously. Mutations are small deletions or point mutations frequently affecting splice sites. Moreover, a 16.7-kb genomic deletion of the 3' end of the gene, most likely a result of recombination between two LINE elements, was identified. The most frequently found mutation, identified in three unrelated Turkish A-T individuals, was previously described to be a Turkish A-T founder mutation. The presence of a founder mutation among relatively small ethnic population groups in Western Europe could indicate a high carrier frequency in such communities. In patients of Dutch ethnic origin, however, no significant founder effect could be identified. The observed genetic heterogeneity including the relative high percentage of splice-site mutations had no reflection on the phenotype. All patients manifested classical A-T and increased cellular radioresistant DNA synthesis.
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PMID:ATM germline mutations in classical ataxia-telangiectasia patients in the Dutch population. 979 9

Effects of different end sequences on stability, circular dichroism spectra (CD), and enzyme binding properties were investigated for six 22-base pair, non-self-complementary duplex DNA oligomers. The center sequences of these deoxyoligonucleotides have 8-14 base pairs in common and are flanked on both sides by sequences differing in context and A-T content. Temperature-induced melting transitions monitored by differential scanning calorimetry (DSC) and ultraviolet absorbance were measured for the six duplexes in buffered 115 mM Na(+) solutions. Values of the melting transition enthalpy, DeltaH(cal), and entropy, DeltaS(cal), were obtained directly from DSC experiments. Melting transition parameters, DeltaH(vH) and DeltaS(vH), were also estimated from van't Hoff analysis of optical melting curves collected as a function of DNA concentration, assuming a two-state melting transition. Melting free energies (20 degrees C) of the six DNAs evaluated from DSC experiments ranged from -18.7 to -32.7 kcal/mol. van't Hoff estimates of the free energies ranged from -18.5 to -48.0 kcal/mol. With either method, the trends in free energy as a function of sequence were identical. Equilibrium binding by BamHI restriction endonuclease to the 22-base pair DNAs was also investigated. The central eight base pairs of all six molecules, 5'-A-GGATCC-A-3', contained a BamHI recognition sequence bounded by A-T base pairs. Magnesium free binding assays were performed by titering BamHI against a constant concentration of each of the deoxyoligonucleotide substrates and analyzing reaction products by gel retardation. Binding isotherms of the total amount of bound DNA versus protein concentration were constructed which provided semiquantitative estimates of the equilibrium dissociation constants for dissociation of BamHI from the six DNA oligomers. Dissociation constants ranged from 0.5 x 10(-)(9) to 12.0 x 10(-)(9) M with corresponding binding free energies of -12.5 to -10.6 (+/-0. 1) kcal/mol. An inverse relationship is found when binding and stability are compared.
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PMID:Thermodynamic, spectroscopic, and equilibrium binding studies of DNA sequence context effects in six 22-base pair deoxyoligonucleotides. 1046 Jan 77


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