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)

The linear virion form of Epstein-Barr virus (EBV) DNA has variable numbers of direct tandem 500 bp repeats at each terminus. The terminal restriction endonuclease fragments and the fused terminal fragments in the intracellular episomal form are heterogeneous in size, and vary by increments of 500 bp. The structure of the termini of EBV in carcinomas of the nasopharynx and the parotid gland was compared with the EBV termini in monoclonal and polyclonal tissues or cell lines. A single band representing the EBV joined termini was detected in each of the carcinomas and in the monoclonal lymphoid proliferations. Polyclonal cell lines contained multiple forms of the joined termini. The detection of a homogeneous episomal population suggests that EBV-associated epithelial malignancies are clonal expansions of a single EBV-infected progenitor cell.
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PMID:The structure of the termini of the Epstein-Barr virus as a marker of clonal cellular proliferation. 302 42

A genomic library of meningococcal DNA from a clinical isolate of Neisseria meningitidis was constructed in the expression vector lambda gt11. Outer membrane complex was prepared from the same strain and used to immunize rabbits to raise polyclonal anti-outer membrane complex serum. The amplified library was probed with this polyclonal serum, and seven expressing recombinants were isolated; further investigations indicated these to be identical. The expressed meningococcal gene in these recombinants was fused to vector beta-galactosidase and shown to encode epitopes present on the 42-kilodalton class 1 outer membrane protein. Estimation of the size of the recombinant fusion protein suggests that up to 40 kilodaltons of protein-coding sequence is present. The lambda gt11 recombinant contains a 3.4-kilobase DNA insert, which has been recloned into a plasmid and characterized by restriction endonuclease analysis. A restriction fragment from the insert, representing the protein-coding region hybridizes to a single 2.2-kilobase XbaI fragment from the homologous strain and to similar-sized XbaI fragments in other strains of meningococci, expressing antigenically distinct class 1 proteins.
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PMID:Molecular cloning and expression of Neisseria meningitidis class 1 outer membrane protein in Escherichia coli K-12. 311 90

A Haemophilus influenzae strain (T-1,3) possessing clinical beta-lactam resistance due to altered penicillin-binding protein 3 was used to construct a recombinant cosmid gene bank in Escherichia coli. Three of the recombinant cosmids were capable of transforming a susceptible H. influenzae strain (Rdnov) simultaneously to moxalactam resistance and altered the binding of penicillin-binding proteins 3a and 3b to [35S]penicillin G. Restriction endonuclease mapping of one of the recombinant cosmids, pLB100, was performed to facilitate subsequent subcloning of the gene(s) responsible for the altered penicillin-binding protein 3 (a and b) binding phenotype. Subcloning of individual fragments derived from pLB100 indicated that two adjacent fragments of DNA were both capable of transforming a susceptible Haemophilus strain to moxalactam resistance and altered penicillin-binding protein 3 binding. Expression of plasmid-coded proteins in minicells indicated that one fragment coded for a major 55,000-molecular-weight polypeptide and that the second contained a C-terminal coding region that expressed a 28,000-molecular-weight polypeptide when fused to the N-terminal region of the tetracycline resistance gene. Initial attempts at labeling the plasmid-coded proteins expressed in minicells with [35S]penicillin G were unsuccessful.
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PMID:Cloning and expression of genes responsible for altered penicillin-binding proteins 3a and 3b in Haemophilus influenzae. 355 33

Cultured human and embryonic chick fibroblasts possess different enzyme-mediated processes to repair cyclobutyl pyrimidine dimers induced in their deoxyribonucleic acid (DNA) by ultraviolet (UV) radiation. While dimers are corrected in human cells by excision repair, a photoenzymatic repair process exists in embryonic chick cells for the removal of these potentially deleterious UV photoproducts. We have utilized a sensitive enzymatic assay to monitor the disappearance, i.e. repair, of dimer-containing sites in fused populations of human and chick cells primarily consisting of multinucleate human/chick heterokaryons. Fused cultures were constructed such that UV photoproducts were present only in chick DNA when evaluating excision repair and only in human DNA when evaluating photoenzymatic repair. Based on the kinetics of site removal observed in these cultures we are led to conclude the following: Within heterokaryons per se the photoreactivating enzyme derived from chick nuclei and at least one excision-repair enzyme (presumably a UV endonuclease) derived from human nuclei act on UV-damaged DNA in foreign nuclei with an efficiency equal to that displayed toward their own nuclear DNA. Hence, after cell fusion these chick and human repair enzymes are apparently able to diffuse into foreign nuclei and once therein competently attack UV-irradiated DNA independently of its origin. In harmony with the situation in nonfused parental cultures, in heterokaryons the chick photoenzymatic repair process rapidly removed all dimer-containing sites from human DNA including the residual fraction normally acted upon slowly by the human excision-repair process.
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PMID:DNA repair in human/embryonic chick heterokaryons. Ability of each species to aid the other in the removal of ultraviolet-induced damage. 447 28

The structure and function of recombinant plasmid pNP5, which consists of vector pMB9 and a 2.5 kb EcoRI fragment harbouring the Escherichia coli uvrB gene, has been investigated. Insertional inactivation with the transposons Tn1 (Apr) or Tn5 (Kmr) has been used to determine the region on pNP5 DNA that is essential for UV resistance in uvrB deletion strains. This region spans approx. 1.8 kb and is separated by at least 280 bp from the pMB9 promoter to which it has been fused. Furthermore, a procedure is described to eliminate the polarity exerted by the transposon Tn5. A combination of in vitro digestion of pNP5::Tn5 DNA with restriction endonuclease XHoI, followed by ligation and subsequent in vivo propagation of the resulting plasmid DNA yields predominantly pNP5 molecules with a site-specific nonpolar mutation. The method allows an investigation of cloned complex genetic units, such as operons.
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PMID:Relief of polarity caused by transposon Tn5: application in mapping a cloned region of the Escherichia coli uvrB locus essential for UV resistance. 626 May 90

Tumor specimens from patients with adenocarcinoma of the colon or rectum were examined for the presence of cytomegalovirus (CMV), and specimens of normal mucosa from the same patients were studied in parallel. Frozen sections of 14 specimens were made and the presence of CMV mRNA assayed by in situ hybridisation using 3H-labelled CMV-DNA as a probe. Nine of these sections were also tested for cytomegalovirus antigens by immunofluorescence. No viral nucleic acids or antigens were detected. In addition to these direct approaches, the specimens were disaggregated and 19 were successfully cultured in various media over several months without yielding virus on any occasion. Areas containing epithelial cells were found in some cultures, foci of bipolar cells in others, while, in several, fibroblastic cells predominated. To ensure that any virus-containing cells were not lost by this method, the disaggregated tumour and normal intestinal cells were directly co-cultivated and also fused with human embryo lung cells, which are permissive for cytomegalovirus replication. The resulting cultures were examined over two to three months for the presence of cytomegalovirus, and in no instance was virus found, despite attempted induction by iododeoxyuridine. Two fusion cultures became contaminated with cytomegalovirus, strain AD-169, which was being handled in the laboratory at the same time. The strain was identified by the pattern of viral DNA fragments produced by restriction endonuclease cleavage. Thus the accidental passage of virus in the heterokaryons did not alter its DNA and would further indicate the absence of any cytomegalovirus genomes in the adenocarcinoma cells.
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PMID:Lack of association of cytomegalovirus with adenocarcinoma of the colon. 627 66

The unintegrated viral DNA intermediates of colobus type C virus (CPC-1) were isolated from infected human cells that were permissive for viral growth. There were two major species of DNA, linear molecules with two copies of the long terminal repeat and relaxed circles containing only a single long terminal repeat. In addition, there was a minor species (approximately 10%) composed of relaxed circles with two copies of the long terminal repeat. A restriction endonuclease map of the unintegrated DNA was constructed. The three EcoRI fragments of circular CPC-1 DNA were cloned in the EcoRI site of lambda gtWES . lambda B and then subcloned in the EcoRI site of pBR322. Using these subgenomic fragments as probes, we have characterized the endogenous viral sequences found in colobus cellular DNA. They are not organized in tandem arrays, as is the case in some other gene families. The majority of sequences detected in cellular DNA have the same map as the CPC-1 unintegrated DNA at 17 of 18 restriction endonuclease sites. There are, however, other sequences that are present in multiple copies and do not correspond to the CPC-1 map. They do not contain CPC-1 sequences either in an altered form or fused to common nonviral sequences. Instead, they appear to be derived from a distinct family of sequences that is substantially diverged from the CPC-1 family. This second family of sequences, CPC-2, is also different from the sequences related to baboon endogenous type C virus that forms a third family of virus-related sequences in the colobus genome.
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PMID:Colobus type C virus: molecular cloning of unintegrated viral DNA and characterization of the endogenous viral genomes of Colobus. 628 75

The P3J-HR-1 strain of Epstein-Barr virus (EBV) fails to immortalize human lymphocytes. We wished to understand the nature of the genomic alterations which correlated with the loss of this ability. As a first step, the heterogeneity of DNA molecules in the P3J-HR-1 line was eliminated by cell cloning. Then a physical map was prepared of virion DNA from one cell clone, designated FF452-3. By comparison with the genomes of two EBVs, B95-8 and FF41, which are competent to immortalize lymphocytes, we identified a total of eight modifications of BamHI and EcoRI restriction endonuclease fragments of EBV (FF452-3) DNA consisting of insertions, deletions, or loss of a restriction endonuclease recognition site. To determine which of these alterations might be responsible for the loss of transforming phenotype, we examined homologous DNA fragments of the Jijoye strain of EBV, the progenitor of the HR-1 strain which still retains the ability to immortalize lymphocytes. We also studied viral DNA in lymphocytes transformed in vitro by Jijoye virus. Six of the eight alterations were found both in Jijoye and in clonal HR-1 DNA and were presumably genomic traits characteristic of this lineage of EBV. A small deletion in the BamHI-K fragment of HR-1 DNA was not found in Jijoye virion DNA, but this deletion was present in intracellular Jijoye DNA. Thus only one major genomic lesion in HR-1 DNA, a deletion of at least 2.4 x 10(6) molecular weight of DNA from a fused BamHI-H-Y fragment, consistently distinguished Jijoye DNA from its non-immortalizing P3J-HR-1 derivative. This deletion is likely to affect EBV genes which are directly or indirectly involved in immortalizing lymphocytes.
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PMID:Non-immortalizing P3J-HR-1 Epstein-Barr virus: a deletion mutant of its transforming parent, Jijoye. 629 33

The integration of 32P-labeled infecting Mu DNA into the Escherichia coli chromosome was investigated. Cleavage of the integrated Mu DNA with restriction endonuclease EcoRI, which cuts twice in the Mu genome, liberated the internal EcoRI fragment but not the left and right end fragments. The ends of the Mu genome became fused with host DNA at a variety of locations generating a smear of radioactive DNA fragments following cleavage with EcoRI. The predominant integration end products of infecting Mu DNA molecules are therefore generated by a mechanism which results in simple insertions and not cointegrates. Since predominantly simple insertions are found after infection (during lysogenization or lytic growth) but not after prophage induction, the transposition mode which is utilized appears to be a function of the source of the transposing DNA. Use of the integrated, 32P-labeled Mu DNA as a hybridization probe with the separated strands of Mu DNA or lambda phages carrying various regions of Mu showed no strand preference in the integration process. Both labeled DNA strands at both ends of the Mu genome were integrated. These results suggest the lack of a site-specific recombination site in the genome; the simple insertions which are the end products of Mu DNA integration following infection appear to be generated by a separate pathway rather than by the resolution of cointegrate structures.
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PMID:Predominant integration end products of infecting bacteriophage Mu DNA are simple insertions with no preference for integration of either Mu DNA strand. 630 98

Many immunoglobulin (Ig)-producing cells retain the DNA that separates Ig variable (V) and constant (C) region genes in the germline. This "remnant" DNA must be moved during the recombination process that joins V and C genes via a joining (J) segment. We have analyzed remnant DNAs in several Ig-producing cell lines. The nucleotide sequences of kappa (kappa) light chain remnant DNAs indicate close relationships to V-J joining. We find fused V kappa and J kappa recognition sequences in five remnant DNAs, suggesting reciprocal relationships to the fused V kappa and J kappa segments produced by V-J joining. However, of sixteen plasmacytoma remnant DNAs analyzed, all involve only recombination with J kappa l. Thus, in most cell lines, remnant DNAs are not directly reciprocal to recombined kappa-genes. On the other hand, our analyses of some myelomas do indicate indirect relationships between remnant DNAs and kappa-genes. Our results suggest that multiple steps of DNA recombination occur during Ig-gene rearrangement. Because remnant DNA joining sites do not exhibit the flexibility that has been observed in Ig-gene V-J joining, our findings also suggest that the joining mechanism may involve endonuclease, exonuclease and ligase activities.
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PMID:Immunoglobulin gene 'remnant' DNA--implications for antibody gene recombination. 632 16


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