Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A DNA-repair endonuclease has been purified 117-fold from mouse plasmacytoma cells (line MPC-11) by gel filtration, followed by ion-exchange and affinity chromatography. Its molecular weight was determined by gel filtration to be 28,000 +/- 2000. The enzyme recognizes apurinic and apyrimidinic sites induced by acid and gamma-rays in DNA, as well as another type of lesion(s) which is introduced into DNA by both ultraviolet irradiation and OsO4. Quantitative measurements of the number of nicks the purified DNA-repair endonuclease makes in DNA treated with various amounts of OsO4 and ultraviolet light suggests that the endonuclease may act on 5,6-dihydroxydihydrothymine lesions. The endonuclease activity was sensitive to the ionic strength and was most active in the presence of 100 mM KCl, whereas the presence of divalent cations did not stimulate the activity.
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PMID:Purification and properties of a mouse-cell DNA-repair endonuclease, which recognizes lesions in DNA induced by ultraviolet light, depurination, gamma-rays, and OsO4 treatment. 625 66

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

An activity has been purified 350-fold from extracts of mouse plasmacytoma cells that forms 5-hydroxymethyluracil (alpha-hydroxythymine) and apyrimidinic sites with phage SPO1 DNA, which contains this base in place of thymine. This DNA glycosylase presumably functions to eliminate hydroxymethyluracil, a major thymine-derived DNA lesion produced by ionizing radiation and oxidative damage. The enzyme has no cofactor requirement and is active in EDTA. Neither intermediate formation nor hydrolysis of hydroxymethyl-deoxyuridine or hydroxymethyldeoxyuridine monophosphate was detected. The enzyme does not cleave apyrimidinic sites in DNA. It does release uracil from the uracil-containing DNA of phage PBS2, but this activity is less than 2% of the predominant uracil DNA glycosylase activity of the cell, which is separated by phosphocellulose chromatography. The major uracil DNA glycosylase does not release hydroxymethyluracil from SPO1 DNA. The hydroxymethyluracil glycosylase is also separated upon phosphocelluose chromatography from a thymine glycol DNA glycosylase activity that is accompanied by an apyrimidinic endonuclease activity.
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PMID:Hydroxymethyluracil DNA glycosylase in mammalian cells. 658 76

The organization of mouse immunoglobulin heavy chain genes has been investigated by hybridization with cloned mu and alpha cDNA probes. Restriction endonuclease fragments bearing mu and alpha constant region genes and two types of variable region (VH) genes were compared in BALB/c embryos, liver and nine plasmacytomas synthesizing IgM, IgA, IgG1, IgG2a, IgG2b and IgG3. Embryo DNA was found to contain a single copy of the C mu gene per haploid genome. In contrast, one VH probe (HPC 76) detected at least six related VH genes, while the other (S107) detected a separate set of at least four genes, indicating that the germline contains distinct sets of multiple related VH genes. Most VH genes within the two subsets remained in germline context in different plasmacytomas, providing no evidence for somatic reassortment of VH genes. One plasmacytoma was devoid of specific VH genes, including some related to the expressed VH sequence. This may mean that the translocation event creating an active heavy chain gene involves deletion of the DNA between the expressed VH and CH sequences. The context of C mu sequences in DNA from a plasmacytoma secreting IgM differed from that in embryo DNA, as did C alpha sequences in two IgA- and several IgG-secreting plasmacytomas. Unlike heavy chain expression, rearrangement was not confined to one allele and often took different forms within a single cell line, presumably varying on different homologous chromosomes. Each rearrangement, whether resulting in an active C gene or not, appeared to change sequences upstream but not downstream from the CH gene. Significantly, the eight IgG and IgA plasmacytomas examined had undergone deletions of at least half and often all C mu sequences while retaining the embryo level of C alpha sequences. Hence a deletion mechanism may be responsible for the switch in expression from one CH gene to another which occurs during differentiation of a lymphocyte clone.
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PMID:Deletions are associated with somatic rearrangement of immunoglobulin heavy chain genes. 676 10

To elucidate the structure of the gene for the constant region of immunoglobulin mu chains, we have cloned a 9.9-kilobase-pair fragment of mouse DNA bearing a gene for the constant region of the mu chain (C mu gene) from an IgM-secreting mouse plasmacytoma. The sequence around this gene has apparently undergone somatic rearrangement; the gene occurs in an EcoRI restriction endonuclease fragment of a different size from that in embryo or liver DNA and no C mu-bearing fragment of embryo size remains in the plasmacytoma. The cloned sequence lacks a variable region gene; hence, if this C mu gene is active, its position within the clone indicates that the gene for the variable region of a heavy chain (VH gene) must be more than 3.7 kilobase pairs away. The C mu gene is divided by three intervening sequences into four coding segments, each of which encodes one of the domains (homology units) of the polypeptide. The nucleotide sequence coding for amino acids near the V-C junction is not present within the C mu clone or clones bearing homologous embryonic VH genes. This suggests that an immunoglobulin heavy chain, in common with light chains, is encoded not only by a V and C gene, but also by an independent joining region (JH) gene.
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PMID:Intervening sequences divide the gene for the constant region of mouse immunoglobulin mu chains into segments, each encoding a domain. 676 39

The incidence of apoptotic and necrotic cell death was compared in CHO, SF9 insect cells and murine plasmacytoma (J558L) and hybridoma (TB/C3) cells during in vitro cultivation in batch cultures. Acridine orange staining and fluorescence microscopy enabled the visualization of a classic morphological feature of apoptotic cell, the presence of condensed and/or fragmented chromatin. DNA gel electrophoresis was employed to show an additional characteristic of the process, the endonuclease-mediated fragmentation of DNA into multiples of 180 base pairs. The levels of apoptosis at the end of batch cultures of plasmacytoma and hybridoma cell lines were found to be 60% and 90% of total dead cells, respectively. However, employing the above-mentioned techniques, the biochemical and morphological features of apoptosis were not found in CHO and SF9 insect cells. Some factors affecting the induction of apoptosis during the batch culture of the hybridoma and plasmacytoma cell lines were identified. The most effective inducer was found to be glutamine limitation, followed by (in order of importance) serum limitation, glucose limitation, and ammonia toxicity. Blockage of the cell cycle of the plasmacytoma and hybridoma cells using thymidine resulted in the induction of apoptosis. This has important implications for the development of cell culture processes that minimize cell division and thereby increase specific productivity.
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PMID:Cell death in bioreactors: a role for apoptosis. 1861 32


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