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)

A DNA methyltransferase was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1. The enzyme recognized the sequence GATC and methylated deoxyadenosine solely in GATC sequences. Host DNA, which contains GATC sequences, but not PBCV-1 DNA, which contains GmATC sequences, was a good substrate for the enzyme in vitro. The DNA methyltransferase activity was first detected about 1 h after viral infection; PBCV-1 DNA synthesis and host DNA degradation also began at about this time. The appearance of the DNA methyltransferase activity required de novo protein synthesis, and the enzyme was probably virus encoded. Methylation of DNAs with the PBCV-1-induced methyltransferase conferred resistance of the DNAs to a PBCV-1-induced restriction endonuclease enzyme described previously (Y. Xia, D. E. Burbank, L. Uher, D. Rabussay, and J. L. Van Etten, Mol. Cell. Biol. 6:1430-1439). We propose that the PBCV-1-induced methyltransferase protects viral DNA from the PBCV-1-induced restriction endonuclease and is part of a virus-induced restriction and modification system in PBCV-1-infected Chlorella cells.
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PMID:DNA methyltransferase induced by PBCV-1 virus infection of a Chlorella-like green alga. 353 3

We have determined the structure of host DNA and viral DNA at the site of integration of Simian virus 40 (SV40) in a line of transformed Balb/c-3T3 cells (SVB400) isolated by single cell cloning after virus infection. Recombinant phage containing integrated viral DNA and flanking host DNA were purified from a genomic library and, in conjunction with restriction endonuclease cleavage analysis of the transformed cell DNA, were used to determine the organization of the integrated viral sequences. There is heterogeneity in the arrangement of the viral sequences resulting from tandem duplications of all or part of the SV40 genome with preservation of the viral-host junctions. The predominant arrangement is the result of tandem duplication of 41% of the SV40 genome from 0.64 to 0.23. Analysis of the structure of integrated viral DNA in SVB400 at different passage numbers and in single cell clones derived from the 20th passage indicated that rearrangements of viral DNA occur after the integration event and continue with passage of the cells. The organization of host sequences before and after the integration of SV40 was determined by restriction endonuclease cleavage analysis of parental 3T3 DNA and SVB400 DNA, and by analysis of recombinant phage isolated from genomic libraries. A deletion of at least 15 X 10(3) bases of host DNA occurred at the site of integration, which indicates that viral integration was not a result of a simple insertion of SV40. Nucleotide sequence analysis of the virus-host junctions showed that retained SV40 sequences were colinear with the viral genome, and that the junctions with SV40 DNA occurred at nucleotide numbers 1377 and 3610. There was no evidence of duplications of viral or host sequences at the junctions, and a comparison of the flanking mouse sequences with the deleted SV40 sequences revealed no significant homology at the point of joining of the two genomes.
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PMID:Rearrangements of host and viral DNA in mouse cells transformed by simian virus 40. 608 79

Influenza virus infection has adverse effects on the metabolism of two representative RNA polymerase II transcripts in chicken embryo fibroblasts, those coding for beta-actin and for avian leukosis virus (ALV) proteins. Proviral ALV DNA was integrated into host cell DNA by prior infection with ALV. Within 1 h after influenza virus infection, the rate of transcription of beta-actin and ALV sequences decreased 40 to 60%, as determined by labeling the cells for 5 min with [3H]uridine and by in vitro, runoff assays with isolated nuclei. The transcripts that continued to be synthesized did not appear in the cytoplasm as mature mRNAs, and the kinetics of labeling of these transcripts strongly suggest that they were degraded in the nucleus. By S1 endonuclease assay, it was confirmed that nuclear ALV transcripts disappeared very early after infection, already decreasing ca. 80% by 1 h postinfection. A plausible explanation for this nuclear degradation is that the viral cap-dependent endonuclease in the nucleus cleaves the 5' ends of new polymerase II transcripts, rendering the resulting decapped RNAs susceptible to hydrolysis by cellular nucleases. In contrast to the nuclear transcripts, cytoplasmic beta-actin and ALV mRNAs, which are synthesized before infection, were more stable and did not decrease in amount until after 3 h postinfection. Similar stability of cytoplasmic host cell mRNAs was observed in infected HeLa cells, in which the levels of actin mRNA and two HeLa cell mRNAs (pHe 7 and pHe 28) remained at undiminished levels for 3 h of infection and decreased only slightly by 4.5 h postinfection. The cytoplasmic actin and pHe 7 mRNAs isolated from infected HeLa cells were shown to be translated in reticulocyte extracts in vitro, indicating that host mRNAs were not inactivated by a virus-induced modification. Despite the continued presence of high levels of functional host cell mRNAs, host cell protein synthesis was effectively shut off by about 3 h postinfection in both chicken embryo fibroblasts and HeLa cells. These results are consistent with the establishment of an influenza virus-specific translational system that selectively translates viral and not host mRNAs.
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PMID:Metabolism and expression of RNA polymerase II transcripts in influenza virus-infected cells. 609 46

It is well established that vaccinia virus infection induces the synthesis of virus-specific DNA in cytoplasmic 'factories', which are sites of virus-specific transcription. The present study demonstrates that vaccinia virus-specific DNA is synthesized also in the nuclei of infected cells with a similar time course. Direct observation and radiolabelling confirm the integrity of isolated nuclei. Reconstitution experiments and inhibitor studies demonstrate that virus-induced DNA is synthesized de novo within nuclei and does not result from cytoplasmic contamination. Cell-specific DNA synthesis is inhibited completely after infection and nuclei of infected cells then synthesize DNA which co-sediments with virus genomic DNA in denaturing gradients. Restriction endonuclease cleavage and hybridization with a virus-specific probe indicate that this is full-length, virus genomic DNA. The biological implications of this are discussed.
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PMID:Synthesis of full-length, virus genomic DNA by nuclei of vaccinia-infected HeLa cells. 622 2

A cDNA transcript of Rous sarcoma virus, which contained the long terminal repeat (LTR) and some additional 3'-terminal sequences, was inserted into the plasmid pBR322. This recombinant plasmid, p53, was then used as a hybridization probe to detect viral terminal sequences in DNA from a number of tissues of birds with a variety of avian leukosis virus (ALV)-induced proliferative diseases. Using restriction endonuclease digestion and blot hybridization analysis, we detected, in addition to standard ALV genomes, viral terminal sequences linked to host DNA and not to viral genes. In DNA from bursal lymphomas and nephroblastomas, we observed small numbers of integration sites occupied by sequences in p53 and lacking most or all of the remainder of the viral genome. In DNA from osteopetrosis, we observed apparently multiple copies of molecules containing host DNA linked to viral LTR sequences. Some of these structures were contained in discrete, probably unintegrated, DNA molecules. We concluded that viral LTR sequences can be inserted as independent elements during recombination with host DNA in some forms of interaction between exogenous retroviruses and host cells. Because the LTRs have been implicated in integration and transcription of viral genes, the possibility that translocation or activation, or both, of host genes may occur as a consequence of viral infection is reinforced by these observations.
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PMID:Independent recombination between avian leukosis virus terminal sequences and host DNA in virus-induced proliferative disease. 626 28

The infection of cultured human cells with baboon endogenous virus (BEV) frequently leads to an association of viral DNA with a specific genetic locus (termed BEVI, for baboon endogenous virus infection) on chromosome 6. Restriction endonuclease digestion of DNA from BEV-infected human cells and their derived somatic cell clones frequently revealed a common cellular DNA sequence in the proximity of one of the junctions between cellular DNA and the integrated virus. We propose that a short cellular DNA sequence, repeated on chromosome 6 and separated by unique DNA sequences, presents a high-affinity target for the integration of BEV in human cells.
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PMID:Targeted integration of baboon endogenous virus in the BEVI locus on human chromosome 6. 640 43

Immunoprecipitation was used to identify adenovirus type 2 (ad2) tumor antigens synthesized in vivo. The antisera, prepared from tumor-bearing animals, reacted with a wide spectrum of ad2 early proteins including a 11 000-dalton (11 K) polypeptide. The gene for this polypeptide was mapped to the transforming region of the viral genome by hybridization selection followed by in vitro translation and immunoprecipitation. Hybrid arrest translation revealed that the 11 K RNA was transcribed from the leftward reading strand (1-strand) in contrast to other mRNAs from this region. Sucrose gradient analysis of the selected 11 K mRNA revealed that the size of the mRNA was 20S corresponding to approximately 2000 nucleotides. Novel 1-strand transcripts of this length from the transforming region were identified by S1 endonuclease analysis. Taken together, these results suggest that both strands of the transforming region of ad2 DNA are actively transcribed into functional mRNA early after viral infection.
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PMID:A novel mRNA and a low molecular weight polypeptide encoded in the transforming region of adenovirus DNA. 698 56

Adenovirus uncouples DNA replication from polyamine biosynthesis and causes chromosome aberrations in rodent cells. Addition of polyamines protected infected cells from this chromosome damage. Spermine was the only individual polyamine which protected. The diamine oxidase inhibitor aminoguanidine also protected. Neither compound detectably reduced synthesis of viral early proteins. The protective effects of spermine and aminoguanidine were not additive. Maximal protection was obtained when the compounds were added 4.5 h before mitosis, but significant protection was observed up to 1.25 h before mitosis. This suggests that the compounds act in G2. In vitro, spermine bound strongly to DNA and protected it from mild endonuclease attack, but aminoguanidine did neither. We propose that viral infection causes a deficiency in spermine during a critical period G2, possibly accompanied by an increase in endonuclease activity. The resulting chromosome damage can be prevented by adding exogenous spermine, or by inhibiting the oxidative degradation of endogenous spermine.
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PMID:Spermine and aminoguanidine protect cells from chromosome aberrations induced by adenovirus during the G2 phase of the cell cycle. 707 55

The process of cell death caused by influenza virus infection in cultured MDCK and HeLa cells was analysed. This infection gave rise to nuclear fragmentation and chromatin condensation accompanied by chromosomal DNA fragmentation into oligonucleosomes. Chromosomal DNA fragmentation progressed concomitantly with cell lysis of MDCK cells and HeLa cells, producing high and low yields of virus particles, respectively, indicating that the extent of cell lysis was not proportional to the virus production. The endonuclease inhibitor zinc blocked DNA fragmentation in MDCK cells. Cycloheximide inhibited DNA fragmentation as well as cell lysis. Inhibition occurred when the drug was added to the medium within 2 h after infection but not efficiently at 4 h or later. Infection induced the Fas Ag gene, which encodes a possible apoptosis-mediating molecule, in the early infectious stage followed by the expression of Fas Ag on the cell surface. These results suggested that influenza virus infection causes apoptotic death of cultured cells, and their fate might be determined at an early stage of the infection by induction of an apoptotic gene.
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PMID:Induction of programmed cell death (apoptosis) by influenza virus infection in tissue culture cells. 750 71

Restriction endonuclease HindIII was purified from Haemophilus influenzae Rd. Two active fractions, P1 and P2, were obtained in phosphocellulose chromatography. HindIII could be purified completely from the first fraction, P1, by subsequent DEAE-cellulose chromatography. The second fraction, P2, showed HindIII activity higher than that of P1, though it was still contaminated with some minor proteins. The HindIII in P2 fraction showed differences in stability, binding to substrate DNA, electrophoretic mobility, etc., from the HindIII in P1 fraction. It is likely that there are two forms of HindIII in the bacterial cell. The endonuclease HindIII in P2 fraction was finally purified by DNA-cellulose chromatography, though considerable loss of enzymatic activity resulted. Upon infection of the cells with phage T4, the P2 fraction in phosphocellulose chromatography almost disappeared. The presence of two forms of HindIII may be related to bacterial defense against viral infection.
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PMID:Two forms of restriction enzyme HindIII. 770 18


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