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)

Ten murine leukemia virus (MuLV)-related DNA sequences were isolated from C3H/HeN mouse genomic DNA by cloning of EcoRI fragments in a Charon 4A vector. Detailed restriction endonuclease maps of four of the clones were developed by using AKR MuLV [32P]cDNA as a probe. C3H clone 14-9 contains approximately 7 kilobase pairs of MuLV-related DNA, one copy of an MuLV long terminal repeat-like sequence, and a region of flanking mouse DNA. C3H clones 34.2 and 36.1 contain approximately 2 kilobase pairs of MuLV-related DNA, one copy of a MuLV LTR-like sequence, and differing lengths of flanking mouse DNA sequences. C3H clone 8.13 was found to contain an insert of 5.7 kilobase pairs of MuLV-related DNA with two long terminal repeat-like regions and sequences which are partially homologous to AKv-1. Comparison fo the restriction endonuclease cleavage maps of these C3H clones with maps recently developed for ecotropic and xenotropic MuLV DNAs indicates that C3H clone 14-9 corresponds to the 5'-terminal portion of a genomic DNA sequence related to xenotropic MuLVs, whereas C3H clones 34.2 and 36.1 correspond to the 3' terminal portions of genomic DNA sequences related to xenotropic MuLVs. Clone 8.13 represents a deleted, xenotropic MuLV-related provirus. C3H clones 14-9, 34.2, 36.1, and 8.13 provide defined DNA sequence probes with which to characterize the organization and expression of endogenous MuLV-related DNA sequences in the mouse genome.
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PMID:Molecular cloning and characterization of murine leukemia virus-related DNA sequences from C3H/HeN mouse DNA. 628 91

Several DNAs representing the genome of the avian acute leukemia virus OK 10 were isolated by molecular cloning from a transformed quail cell line, 9C, which contained at least six OK 10 proviruses. Recombinant lambda phages harboring the OK 10 genome and additional flanking cellular DNA sequences were studied by restriction endonuclease mapping and hybridization to viral cDNA probes. Six of the clones represented complete proviruses with similar, if not identical, viral sequences integrated at different positions in the host DNA. The organization of the OK 10 genome was determined by electron-microscopic analysis of heteroduplexes formed between the cloned OK 10 DNA and DNAs representing the c-myc gene and the genomes of two other avian retroviruses, Rous-associated virus-1 and MC29. The results indicated that the OK 10 proviral DNA is about 7.5 kilobases in size with the following structure: 5'-LTR-gag-delta polmyc-delta env-LTR-3', where LTR indicates a long terminal repeat. The oncogene of OK 10, v-mycOK 10, forms a continuous DNA segment of around 1.7 kilobases between pol and env. It is similar in structure and length to the v-myc gene of MC29, as demonstrated by restriction endonuclease and heteroduplex analyses. Two of the OK 10 proviruses were tested in transfection experiments: both DNAs gave rise to virus with the transforming capacities of OK 10 when Rous-associated virus-1 was used to provide helper virus functions.
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PMID:Avian acute leukemia virus OK 10: analysis of its myc oncogene by molecular cloning. 630 6

A recombinant DNA clone, named AL10, that contains murine leukemia virus (MuLV) related sequences was isolated from BALB/c mouse chromosomal DNA and examined in detail. Restriction endonuclease mapping revealed that the 10.5 kbp EcoRI insert consists of a 3.6 kbp left flanking cellular DNA region and a 6.9 kbp MuLV-related region that has a typical proviral LTR-gag-pol-env structure up to the EcoRI site in the env gene region. Comparison of the AL10 map with ecotropic and xenotropic virus isolates revealed many common restriction sites in the LTR and pol gene regions, but much fewer in the leader and gag regions. A stretch of 1,700 nucleotides containing the cellprovirus junctional region was sequenced and revealed transcriptional consensus signals and other structural features characteristic of MuLV LTRs, as well as two distinctive features: (a) a sequence of approximately 170 bp with direct and inverted terminal repeats not seen in infectious MuLV LTRs was identified in the U3 region between the "enhancer" region and the "CAT" box. This novel segment or its homologous sequences appear to be present in most of the endogenous MuLV-related LTRs and in other chromosomal locations of the mouse (b) The tRNA primer binding site is not complementary to proline tRNA, the primer for all known MuLVs, but is a 17/18 match with rat glutamine tRNA. The integration site of AL10 provirus was in a unique DNA region but contained an "Alu"-like short interdispersed repeat in the 5' adjacent cellular region. The AL10 proviral integration found in BALB/c was also apparent in RFM, AKR and SENCAR mouse cells but not in cells of NFS/N, C3H, HRS/J, SC-1, and a California Lake Casitas wild mouse.
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PMID:A novel sequence segment and other nucleotide structural features in the long terminal repeat of a BALB/c mouse genomic leukemia virus-related DNA clone. 631 May 6

The mouse mammary tumor virus long terminal repeat (MMTV LTR) has been introduced into cultured murine cells, using the 69% transforming fragment of bovine papilloma virus type 1 (BPV). Transformed cells contain up to 200 copies of the chimeric molecules per diploid genome. The restriction endonuclease map of the acquired recombinants, as well as the physical structure of the DNA, indicates that the LTR-BPV molecules present in these cells occur exclusively as unintegrated, extrachromosomal episome. When a 72-base pair direct repeat "enhancer" element (derived from the Harvey sarcoma retrovirus) was included in the MMTV LTR-BPV chimeric plasmids, DNA acquired through transfection, with a single exception, was integrated or rearranged or both. The transcriptional potential of the episomal MMTV promoter present in these cells was tested in two ways. First, steady-state levels of MMTV-initiated RNA were measured by quantitative S1 mapping. Second, the relative number of transcription complexes initiated in vivo was determined by using a subnuclear fraction highly enriched for MMTV-BPV minichromosomes in an in vitro transcription extension assay. Both approaches showed that the MMTV LTR present in the episomal state was capable of supporting glucocorticoid hormone-regulated transcription. We have therefore demonstrated the hormone response for the first time in a totally defined primary sequence environment. Significant differences both in the basal level of MMTV-initiated transcription and in the extent of glucocorticoid induction were observed in individual cell lines with similar episomal copy numbers. These phenotypic variations suggest that epigenetic structure is an important component of the mechanism of regulation.
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PMID:Glucocorticoid regulation of transcription at an amplified, episomal promoter. 631 79

By the use of recombinant DNA technology and microinjection in cultured cells, the molecular genetic elements involved in the evolution of a retrovirus with the multipotential to infect, transform and replicate in host cell, have been critically examined in this investigation. Recently we have identified and purified the integrated and proviral DNA sequences specific for two rat endogenous helper leukemia viruses, WR- RaLV , originated from a chemically induced wild rat fibrosarcoma, and RHHV , isolated from a chemically induced rat hepatoma, HTC-H1 (1). By using a multidisciplinary approach combining restriction endonuclease analysis, reverse phase V-column chromatography, agarose gel electrophoresis, Southern blot transfer and filter nucleic acid hybridization, we were able to demonstrate that the rat helper leukemia viral DNA sequence was approximately 8.4-8.8 kb. The 8.8 kb RHHV DNA was molecularly cloned via the EK-1 certified vector pBR 322 plasmid into E. coli RRI cells. A successful recombinant clone, 8/32, that carried one entire RHHV 8.8 kb DNA sequence was mapped by restriction endonuclease analyses. Restricted DNA fragments of various sizes throughout the complete RHHV genome were isolated and purified for intranuclear microinjection into normal rat kidney cells. Release of type C infectious helper virus in these microinjected cells was investigated by superinfection on K-NRK, Kirsten sarcoma transformed non-producer cells. Recombination of the helper viral DNA sequence, en toto or of subgenomic sizes, carried in microinjected cells, with the sarcomagenic DNA sequence, carried in K-NRK cells, was also studied by genome-rescue and cell-transformation experiments. Our observations led to the conclusion that all critical genetic elements including the 5' LTR helper DNA sequence, gag, pol, and env genes, encoded for the biological activity of the type C helper virus resided within the 6.0 kb proximal to the 5' terminus of the endogenous rat type C helper virus DNA. They proved vitally essential for the recombination with the Src sequence during the evolution of an infectious, transforming and replication-competent retrovirus.
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PMID:Cloning of the rat endogenous helper leukemia virus DNA sequence and expression of the helper activity encoded by the cloned DNA sequence in normal rat kidney cells by microinjection. 632 7

We have isolated homogeneous trp aporepressor from an overproducing strain of Escherichia coli carrying a plasmid containing trpR preceded by tandem trp operon promoters. Dye-affinity and ion-exchange chromatography were used in conjunction with a gel electrophoresis assay in which the repressor, when bound to the trp operator, protects an Rsa I restriction site from endonuclease cleavage. Crystals suitable for x-ray diffraction studies were grown from a variety of concentrated salt solutions. Hydrodynamic properties and electrophoretic analysis of unmodified and covalently crosslinked aporepressor show that the free aporepressor has an isoelectric point of 5.9 and is a dimer containing two identical 12.5-kilodalton subunits in the presence or absence of L-tryptophan. The repressor . operator complex binds poorly to nitrocellulose filters, but restriction-site protection studies indicate that, in the presence of tryptophan, one dimer is bound to the operator site with an apparent dissociation constant less than 2 X 10(-9) M. Preliminary equilibrium dialysis experiments suggest that tryptophan binds to the aporepressor with a dissociation constant of 1.6 X 10(-5) M.
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PMID:Purification and characterization of trp aporepressor. 633 93

The complete amino acid sequence of yeast phosphoglycerate kinase, comprising 415 residues, was determined. The sequence of residues 1-173 was deduced mainly from nucleotide sequence analysis of a series of overlapping fragments derived from the relevant portion of a 2.95-kilobase endonuclease-HindIII-digest fragment containing the yeast phosphoglycerate kinase gene. The sequence of residues 174-415 was deduced mainly from amino acid sequence analysis of three CNBr-cleavage fragments, and from peptides derived from these fragments after digestion by a number of proteolytic enzymes. Cleavage at the two tryptophan residues with o-iodosobenzoic acid was also used to isolate fragments suitable for amino acid sequence analysis. Determination of the complete sequence now allows a detailed interpretation of the existing high-resolution X-ray-crystallographic structure. The sequence -Ile-Ile-Gly-Gly-Gly- occurs twice in distant parts of the linear sequence (residues 232-236 and 367-371). Both these regions contribute to the nucleoside phosphate-binding site. A comparison of the sequence of yeast phosphoglycerate kinase reported here with the sequences of phosphoglycerate kinase from horse muscle and human erythrocytes shows that the yeast enzyme is 64% identical with the mammalian enzymes. The yeast has strikingly fewer methionine, cysteine and tryptophan residues.
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PMID:The complete amino acid sequence of yeast phosphoglycerate kinase. 634 86

Tryptophan-containing peptides, such as Lys-Trp-Lys, Lys-Trp-Gly-Lys and Lys-Gly-Trp-Lys, bind with high affinity to apurinic sites in DNA. The association constant for binding of Lys-Trp-Lys to an apurinic site is two orders of magnitude higher than that for binding to a native site. This is due to a very efficient stacking of tryptophan with the bases on both sides of the vacant apurinic site. When the complexes were incubated at 37 or 45 degrees C a cleavage of the phosphodiester bond was observed. Using pBR 322 DNA containing apurinic sites, conversion of the superhelical to the relaxed circular form was observed as a result of single-strand breakage. The peptide Lys-Gly-Lys had no effect and Lys-Trp-Lys did not induce any cleavage in pBR 322 DNA which did not contain any apurinic site. Therefore, a simple tripeptide, Lys-Trp-Lys, exhibits both the specificity of recognition and the activity of an endonuclease for apurinic sites in DNA.
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PMID:[Recognition and cleavage of apurinic sites in DNA by the tripeptide lysyl-tryptophyl-lysine]. 679 2

R2 is a non-LTR retrotransposable element that inserts at a specific site in the 28S rRNA genes of most insects. We have expressed the open reading frame of the R2 element from Bombyx mori, R2Bm, in E. coli and shown that it encodes both sequence-specific endonuclease and reverse transcriptase activities. The R2 protein makes a specific nick in one of the DNA strands at the insertion site and uses the 3' hydroxyl group exposed by this nick to prime reverse transcription of its RNA transcript. After reverse transcription, cleavage of the second DNA strand occurs. A similar mechanism of insertion may be used by other non-LTR retrotransposable elements as well as short interspersed nucleotide elements.
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PMID:Reverse transcription of R2Bm RNA is primed by a nick at the chromosomal target site: a mechanism for non-LTR retrotransposition. 767 54

Mag is a retrotransposon found as an insert in the Sericin 2 gene. It is present in a few copies--4 to 15--dispersed in the genome of different strains of Bombyx mori as well as in Bombyx mandarina. Flanked by a 5 bp target sequence with no sequence specificity, it is bordered by direct repeats of 77 nucleotides. Despite their unusual short size, these terminal repeats and their immediately adjacent sequences present all the signals necessary for transcription into genomic RNA and for reverse transcription. Mag contains two overlapping open reading frames which are organized as the gag and pol genes of retroviruses and encode putative nucleic acid binding peptide, protease, reverse transcriptase, RNase H and endonuclease in this order. Sequence comparison of these proteins places mag within the gypsy group of LTR retrotransposons next to the echinoderm element SURL.
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PMID:Structural features of mag, a gypsy-like retrotransposon of Bombyx mori, with unusual short terminal repeats. 781 9


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