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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)

Endonuclease activities of cytoplasmic extracts of BSC-1 (E1) and BHK-21-cl 13 (E2) cells were assayed with SV-40 as a substrate and analysed by velocity sedimentation in alkaline and neutral sucrose gradients. Endonucleases were found to require Mg2+ ions for their activity. E1 endonuclease generated linear 6 S DNA fragments, pointing to non-random double-strand cleavage of DNA ; the action of E2 endonuclease resulted in double-strand DNA cleavage to fragments heterogeneous in size. Both endonucleases were inhibited by ATP. The inhibitory effect of actinomycin D (AD) was proportional to the AD/DNA molar ratio. AD+ATP association as well as the presence of ethidium bromide altered the cleavage pattern of E1 towards the predominance of single-strand breaks.
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PMID:Alteration of the cytoplasmic endonuclease cleavage pattern of SV-40 deoxyribonucleic acid in the presence of ATP, actinomycin D and ethidium bromide. 19 89

Nuclear extracts from several tissue culture cell lines (human, primate, and murine) contain an endonuclease that specifically cleaves sequences at the herpes simplex virus 1 (HSV-1) segment inversion site. Mapping studies identified the preferential site of cleavage as a set of tandemly repeated dodecamers, the DR2 repeats. Endonuclease levels vary according to the proliferative state of the cell; little or no activity is detectable in extracts from quiescent cells, whereas high levels are expressed in dividing cells. Also, infection of density-arrested BSC-1 cells with HSV-1 induces a substantial increase (at least 35-fold) in endonucleolytic activity, which is first detectable at about 1 hr after infection at 32 degrees C. The elevated levels of enzyme activity then persist throughout the viral life cycle. In addition to the HSV-1 DR2 repeats, certain other G+C-rich sequences with an asymmetric distribution of purines and pyrimidines on the DNA strands and with appropriate sequences and lengths are substrates for the nuclease. These data indicate that target site recognition by the enzyme is conformation specific rather than sequence specific.
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PMID:The herpes simplex virus 1 segment inversion site is specifically cleaved by a virus-induced nuclear endonuclease. 165 Apr 68

Linker insertion mutants affecting the simian virus 40 (SV40) large tumor (T) antigen were constructed by inserting a 12-base-pair oligonucleotide linker into restriction endonuclease cleavage sites located within the early region of SV40. One mutant, with the insertion at amino acid 5, was viable in CV-1p and BSC-1 cells, indicating that sequences very close to the amino terminus of large T could be altered without affecting the lytic infection cycle of SV40. All other mutants affecting large T were not viable. In complementation assays between the linker insertion mutants and either a late-gene mutant, dlBC865, or a host range/helper function (hr/hf) mutant, dlA2475, delayed complementation was seen with the 6 of the 10 nonviable mutants. Of these 10 mutants, 5 formed plaques 3 to 4 days later than in control complementations, while complementation by one of the mutants, inA2827, with an insertion at amino acid 520, was delayed more than 1 week. Most mutants which showed delayed complementation replicated less well in Cos-1 cells than did a control mutant, dlA1209, which produced no T antigen. The replication of inA2827(aa520) was reduced by more than 90%. Similar interference with viral DNA replication was seen when CV-1, HeLa, or 293 cells were cotransfected with an origin-defective plasmid encoding wild-type large T antigen and with inA2827(aa520). Only one of the mutant T antigens, inA2807(aa303), was unstable. These results indicate that some of the mutant T antigens interfered with functions of wild-type T required for viral DNA replication. However, not all of the mutants which showed delayed complementation also showed interference with viral DNA replication. This indicates that mutant large T antigens may interfere trans dominantly with multiple activities of wild-type large T antigen.
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PMID:Linker insertion mutants of simian virus 40 large T antigen that show trans-dominant interference with wild-type large T antigen map to multiple sites within the T-antigen gene. 255 52

The restriction endonuclease, HindIII, gives rise to three fragments in each of the three mitochondrial DNAs isolated from the established mammalian cell lines LA9 (mouse), HeLa (human), and BSC-1 (African green monkey). The restriction endonuclease, EcoRI, gives rise to three fragments in mitochondrial DNA from HeLa and to two in DNAs from LA9 and BSC-1. The sizes and the orders of the fragments in the respective genomes have been determined with data obtained from the electron microscope. The origin and the direction of replication have been designated in each of the cleavage maps. Polyacrylamide gel electrophoretic analyses demonstrated that additional fragments not detectable in the electron microscope and larger than 50 nucleotide pairs were not present.
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PMID:Restriction endonuclease cleavage maps of animal mitochondrial DNAs. 421 20

DNA transfection of African green monkey BSC-1 cells with simian virus 40 (SV40) DNA and bacterial virus phi X174 replicative form DNA ("cotransfection") yielded stocks containing SV40/phi X174 recombinant virus, which was detected by an infectious-center in situ plaque hybridization procedure and which was sensitive to anti-SV40 antiserum. The recombinant virus replicated during serial passage. Restriction endonuclease cleavage of the SV40/phi X174 DNA indicated that several different types of recombinant DNA structures had arisen. Similar SV40 DNA cotransfection experiments with polyoma virus DNA, bacterial plasmid (pBR322) DNA, and a plasmid-cloned segment of the mouse genome (coding for intracisternal type A particles) yielded stocks that generated recombinant plaques as judged by in situ plaque hybridization with the appropriate labeled probe. It appears, therefore, that an active indiscriminate recombination process, incapable of distinguishing between diverse DNAs of prokaryotic and eukaryotic origin, occurs in SV40-infected monkey cells.
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PMID:Indiscriminate recombination in simian virus 40-infected monkey cells. 625 43

Four independently and newly isolated defective variants of simian virus 40 have been characterized. All four are very similar, if not identical, to two previously and independently isolated variants (Wakamiya et al., J. Biol. Chem. 254:3584-3591, 1979; J. Papamatheakis, E. Kuff, E. Winocour, and M. F. Singer, J. Biol. Chem. 255:8919-8927, 1980). The documented similarities include restriction endonuclease maps and the presence of the same monkey DNA segments covalently linked to simian virus 40 DNA sequences. Each of the newly described variants was first detected upon serial passaging of wild-type simian virus 40 at a high multiplicity of infection at 33 degrees C as recently described (M. F. Singer and R. E. Thayer, J. Virol. 35:141-149, 1980). A variety of experiments support the idea that the various isolates were independent and do not reflect inadvertent cross-contamination. Two of the new isolates arose during passage of wild-type strain 777 virus in BSC-1 cells, one during passage of strain 776 in BSC-1 cells, and one during passage of strain 776 in primary African green monkey kidney cells. The two variants obtained after passage of strain 776 were shown to contain a particular recognition site for restriction endonuclease MboII within their simian virus 40 DNA segments, as do the two previous isolates. This site is not present in wild-type strain 776 DNA but is shown here to be present in wild-type strain 777 DNA. The surprising recurrence of closely related variants and particularly the unexpected presence of the endo R.MboII site in variants derived from passaging strain 776 suggest that these variants may arise by mechanisms other than recombination between the initial infecting viral genome and the host DNA.
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PMID:Recurring defective variants of simian virus 40 containing monkey DNA segments. 626 Sep 83

Simian virus 40 nucleoprotein isolated from the nuclei of infected cells contains a nuclease-sensitive site adjacent to the viral origin of replication (between 0.66 and 0.73 map unit). Nuclear extracts were subfractionated by sucrose gradient centrifugation to yield provirions (200S) and simian virus 40 chromatin (80S). The 80S fraction was cleaved either by DNase I or by an endonuclease endogenous to BSC-1 cells with high preference for the 0.66 to 0.73 region. The 200S fraction was treated to release core particles that were sensitive to nuclease cleavage; however, DNase I showed little or no preference for the 0.66 to 0.73 region of the provirion core nucleoprotein.
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PMID:Nuclease-sensitive sites in the two major intracellular simian virus 40 nucleoproteins. 630 35

Three simian virus (SV40)-phi X174 recombinant genomes were isolated from single BSC-1 monkey cells cotransfected with SV40 and phi X174 RF1 DNAs. The individual cell progenies were amplified, cloned, and mapped by a combination of restriction endonuclease and heteroduplex analyses. In each case, the 600 to 1,000 base pairs of phi X174 DNA (derived from different regions of the phi X174 genome) were present as single inserts, located in either the early or late SV40 regions; the deletion of SV40 DNA was greater than the size of the insert; and the remaining portions of the hybrid genome were indistinguishable from wild-type SV40 DNA, as judged by both mapping and biological tests. Hence, apart from the deletion which accommodates the phi X174 DNA insert, no other rearrangements of SV40 DNA were detected. The restriction map of a SV40-phi X174 recombinant DNA isolate before molecular cloning was indistinguishable from those of two separate cloned derivatives of that isolate, indicating that the species cloned was the major amplifiable recombinant structure generated by a single recombinant-producing cell. The relative simplicity of the SV40-phi X174 recombinant DNA examined is consistent with the notion that most recombinant-producing BSC-1 cells support single recombination events generating only one amplifiable recombinant structure.
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PMID:Structure of simian virus 40-phiX174 recombinant genomes isolated from single cells. 631 Jan 46

A papovavirus was isolated from uninoculated kidney cell cultures of the Cynomolgus Macaque (Macaca fascicularis), in which it produced extensive cytopathologic changes after prolonged periods of culturing. On basis of virion morphology, genome size, and restriction endonuclease data, this virus was identified as a new isolate of the Stump-Tailed Macaque Virus (STMV) and subsequently named CK-strain (Cynomolgus kidney) of STMV. Without inducing c.p.e. the virus replicated also in BSC-1, VERO, human embryonic, and calf kidney cells. The relationship between STMV and SV40 was investigated by cross-blot hybridization between DNA fragments of both viruses. The region containing the SV40 regulating sequences showed strong homology with STMV DNA. No antigenic relationship between STMV and SV40 could be demonstrated. Antibodies to STMV were not found in sera from 20 Cynomolgus Macaques, but were detected in 25 out of 57 cattle sera and 6 out of 26 bovine colostrum samples. The serologic findings indicate that STMV is not a latent simian virus, but a virus of bovine origin.
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PMID:Isolation and characterization of a papovavirus from cynomolgus macaque kidney cells. 632 74

A 300 base-pair (bp) size class of small polydisperse circular DNA (spcDNA) isolated from the BSC-1 line of African Green monkey kidney cells was cleaved with the restriction endonuclease Sau3A, and the resulting fragments (100 to 200 bp) were cloned in bacteriophage M13 mp7. The nucleotide sequence of each of 24 clones containing DNA sequences homologous to the Alu family of mobile, dispersed, repetitive elements was then determined. Analysis of these sequences revealed that many, and perhaps all, of the 300 bp Alu-containing spcDNAs had regions in which the 5' and 3' ends of the normal Alu element were juxtaposed and covalently joined. Although more than one model can explain the generation of such circular molecules, the most attractive one at this time involves their generation from reverse transcripts of Alu-specific RNAs.
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PMID:Some extrachromosomal circular DNAs containing the Alu family of dispersed repetitive sequences may be reverse transcripts. 632 7


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