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 DNA of herpesvirus pan, a primate B-lymphotropic herpesvirus, shares about 40% well-conserved sequence relatedness with Epstein-Barr virus (EBV) and herpesvirus papio DNAs. Labeled cloned fragments from the EBV recombinant DNA library were cross hybridized to blots of EcoRI, XbaI, and BamHI restriction endonuclease fragments of herpesvirus pan DNA to identify and map homologous sequences in the herpesvirus pan genome. Regions of colinear homology were demonstrated between 6 x 10(6) daltons and 108 x 10(6) daltons in the DNAs. The structural organization of herpesvirus pan DNA was similar to the format of Epstein-Barr virus and herpesvirus papio DNAs. The DNA consists of two domains of largely unique sequence complexity, a segment US of 9 x 10(6) daltons and a segment UL of 88 x 10(6) daltons. US and UL are separated by a variable number of tandem repetitions of a sequence IR (2 x 10(6) daltons). There was homology between DNA which mapped at 26 to 28 x 10(6) daltons and 93 to 95 x 10(6) daltons in UL. The terminal reiteration component, TR, of herpesvirus pan DNA and sequences which mapped to the left of 6 x 10(6) daltons and to the right of 108 x 10(6) daltons had no detectable homology with the corresponding regions of Epstein-Barr virus DNA.
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PMID:DNA of herpesvirus pan, a third member of the Epstein-Barr virus-Herpesvirus papio group. 628 82

We used cloned BamHI fragments from Epstein-Barr virus strain B95-8 [EBV(B95-8)]DNA to obtain detailed restriction maps of the region of the genome adjacent to the large internal repeat cluster. These maps together with the results of hybridization experiments using a 3.1-kilobase repeat probe defined more precisely the location of the injection between the internal repeat cluster and the flanking unique-sequence DNA. On one side (UL), the repeat sequences extended 600 +/- 80 base pairs (bp) into BamHI-Y; on the other side (US), they extended 1,300 +/- 200 bp into BamHI-C. Therefore, EBV(B95-8) DNA contained a nonintegral number of 3.1-kilobase repeat units, namely, 12.6 copies. The mapping studies also revealed a second series of internal tandem repetitions in EBV(B95-8) DNA located within the BamHI-H fragment. This cluster comprised 11 copies of a 135-bp repeat unit which contained a single site for the NotI restriction endonuclease. Hybridization to these cloned EBV(B95-8) fragments using total EBV(HR-1) DNA as probe indicated that the deletion in EBV(HR-1) removed all 3,000 bp of unique-sequence DNA which lay between the large 3.1-kilobase and the small 135-bp repeat clusters. Thus, the deletion which destroyed the transforming ability in the EBV(HR-1) virus was bounded on either side by tandem repetitions.
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PMID:Organization of the Epstein-Barr virus DNA molecule. II. Fine mapping of the boundaries of the internal repeat cluster of B95-8 and identification of additional small tandem repeats adjacent to the HR-1 deletion. 628 98

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

Mouse and human DNA used as in vitro-labeled "high-complexity" probes revealed hybridization between specific herpesvirus DNA fragments on Southern transfers and repetitive sequences present at 10(3) to 10(5) copies per mammalian cell genome. Several different sites of major cell-virus sequence homology have been detected in both the herpes simplex virus type 1 and type 2 genomes, and these are located predominantly within the L and S inverted repeat regions and near the center of the L unique region. The hybrids persisted even in relatively stringent conditions, and appear to correlate closely with some of the previously recognized regions of size heterogeneity in the viral genome. Cloned viral DNA fragments from each site hybridized to different sets of discrete bands and dispersed elements within restriction-endonuclease-digested genomic DNA from a variety of vertebrate species. Localized cell-virus homology was also detected in both the human Epstein-Barr virus and cytomegalovirus genomes.
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PMID:Homology between mammalian cell DNA sequences and human herpesvirus genomes detected by a hybridization procedure with high-complexity probe. 629 53

A 1,400-base-pair (bp) region within the BamHI H fragment of Epstein-Barr virus (EBV) (B95-8) DNA consists of a cluster of tandemly duplicated direct repetitions characterized by single sites for the NotI restriction endonuclease. Nucleotide sequencing revealed a 125-bp repeat unit of 84% guanine-plus-cytosine content which is theoretically capable of extensive secondary structure formation. The flanking sequences adjacent to the NotI repeat cluster contained an additional 38-bp portion of repeat unit DNA, thus establishing that EBV(B95-8) contains a nonintegral number of NotI repeats totalling 11.3 copies. Restriction site mapping of the homologous cloned BamHI "H" fragment from the nontransforming EBV (P3HR-1) isolate revealed that a contiguous 6,650-bp region including the entire NotI repeat cluster has been deleted from the BamHI-H, -Y, and -W regions of the P3HR-1 genome. By nucleotide sequencing across the novel junction, we have precisely identified the P3HR-1 deletion boundaries in BamHI-H and the internal repeat and suggest that a complex pattern of direct and inverted partial DNA homologies may have been involved in the original recombination event. The cloned BamHI H fragment and isolated NotI repeat unit have also been used as probes to detect homologous mRNA transcripts in the B95-8 and Raji cell lines of EBV-transformed lymphoblasts. These experiments showed that the NotI repeats form part of the template for a polyadenylated 2.5-kilobase mRNA transcript which becomes much more abundant after 12-O-tetradecanoyl-phorbol-13-acetate treatment of the cultures. The direction of transcription of this mRNA and the nucleotide sequence of most of its template and 5' flanking regions have been determined. The probable promoter for the 2.5-kilobase mRNA initiates transcription efficiently in an in vitro assay and contains several TAATGA-like elements that may be indicative of herpesvirus immediate-early class promoters. The need to repress expression of this gene during latency suggests a possible novel regulatory role for tandem repeat structures inside a eucaryotic virus transcription unit. The deletion in EBV(P3HR-1), which has been associated with the loss of lymphocyte "immortalizing" capacity in this isolate, eliminates part of the coding region as well as the NotI repeats from the 2.5-kilobase mRNA transcript, but the promoter and proximal 340-bp portions of the template remain.
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PMID:Organization of the Epstein-Barr virus DNA molecule. III. Location of the P3HR-1 deletion junction and characterization of the NotI repeat units that form part of the template for an abundant 12-O-tetradecanoylphorbol-13-acetate-induced mRNA transcript. 631 Jan 41

Epstein-Barr virus (EBV)-negative, Burkitt-like lymphoma-derived cells were transformed with a transducing vector (pSV2-gpt) containing the Escherichia coli gene coding for xanthine-guanine phosphoribosyltransferase (XGPRT) and with a derivative of PSV2-gpt that carries the genes for the EBV-associated small RNAs on the EcoRI J fragment of B95-8 EBV DNA inserted at the unique EcoRI site (pJ-gpt). Cells transformed with PSV2-gpt and pJ-gpt express the E. coli gpt gene to approximately the same extent, judged by determinations of the XGPRT activity of cell extracts. Blot hybridisation experiments with restriction endonuclease-cleaved DNA from the transformants have revealed the presence of vector DNA sequences in the cells, at least some of which are most probably integrated into high mol. wt. chromosomal DNA. Northern blot hybridisation analysis of cytoplasmic RNA from pJ-gpt-transformed cells revealed the presence of an EcoRI J DNA complementary RNA species of the same size as the EBV DNA-encoded small RNAs found in EBV-transformed cells.
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PMID:Transfer of the Epstein-Barr virus genes coding for small RNAs to human lymphoid cells with a vector carrying a dominant selectable marker. 631 18

By cloning the HR-1 Burkitt lymphoma line, we previously uncovered two distinct biological variants of nontransforming Epstein-Barr virus (EBV). The most commonly cloned variant has a low rate of spontaneous viral synthesis and is unable to induce early antigen in Raji cells (EAI-). A rare variant spontaneously releases virus which is capable of inducing early antigen in Raji cells (EAI+). Since EAI- virus lacks heterogeneous DNA (het-) and EAI+ virus contains heterogeneous DNA (het+), we suggested that spontaneous viral synthesis and induction of early antigen are biological properties which correlate with the presence of het sequences. The present experiments provide three new lines of experimental evidence in favor of this hypothesis. (i) Revertant subclones of the EAI+ het+ variant which have lost the het DNA concomitantly lost EAI ability. Thus, het DNA is not stably associated with the cells as are the episomes. (ii) het DNA was acquired by two het- subclones of the HR-1 line after superinfection with EAI+ virus. After superinfection, these clones synthesized EAI+ het+ virus. Thus, het DNA may be maintained in the HR-1 line by cell-to-cell spread. (iii) Virus with het DNA activated full expression of endogenous latent EBV of the transforming phenotype in a line of immortalized neonatal lymphocytes designated X50-7. By use of restriction endonuclease polymorphisms unique to both the superinfecting and endogenous genomes, we show that the genome of the activated virus resembles that of the virus which was endogenous to X50-7 cells. This result suggests that het sequences result in transactivation of the latent EBV. het DNA had homology with EBV sequences which are not normally contiguous on the physical map of the genome. het DNA was always accompanied by the presence of DNA of nonheterogenous HR-1. Thus, het DNA is a form of "defective" EBV DNA. However, the biological effect of this defective DNA is to enhance rather than to interfere with EBV replication. This is a novel property of defective virus.
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PMID:Epstein-Barr virus with heterogeneous DNA disrupts latency. 632 89

Bacterially expressed Epstein-Barr virus (EBV) DNase was purified to 98% purity and used as the source for characterization of the enzyme activities. Complete digestion of DNA by EBV DNase yielded 5'-monophosphate nucleosides as the final products. During the logarithmic phase of the reaction, EBV DNase acted processively on dsDNA but distributively on ssDNA. Both 5' to 3' and 3' to 5' exonuclease activities were present, although the former was shown to be 10-fold stronger. No significant discrepancy was seen in the liberation of end-labeled nucleotides by DNase when substrates with 5'-protruding, blunt, or 3'-protruding ends were used. EBV DNase was demonstrated also to have an endonuclease activity using supercoiled plasmid DNA as substrate. Two preferential dsDNA cleavage sites were mapped on pBS-TR, a pBlueScript vector containing one copy of the EBV terminal repeat; both are in vector sequences. Finally, an N-terminally truncated EBV major DNA binding protein, but not EA-D, was shown to inhibit EBV DNase activity. This inhibitory effect may due to direct protein-protein interactions between EBV DNase and the major DNA binding protein. The biological significance of these characteristics is discussed.
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PMID:Characterization of Epstein-Barr virus DNase and its interaction with the major DNA binding protein. 774 43

The Epstein-Barr virus (EBV) origin of plasmid replication (oriP) includes two known cis-acting components, the dyad symmetry region and the family of repeats. We used P1 nuclease, a single-strand-specific endonuclease, to probe EBV oriP for DNA sequences that are intrinsically easy to unwind on a negatively supercoiled plasmid. Selective nuclease hypersensitivity was detected in the family of repeats on an oriP-containing plasmid and in the dyad symmetry region on a plasmid that lacks the family of repeats, indicating that the DNA in both cis-acting components is intrinsically easy to unwind. The hierarchy of nuclease hypersensitivity indicates that the family of repeats is more easily unwound than the dyad symmetry region, consistent with the hierarchy of helical stability predicted by computer analysis of the DNA sequence. A specific subset of the family of repeats is nuclease hypersensitive, and the DNA structure deduced from nucleotide-level analysis of the P1 nuclease nicks is a cruciform near a single-stranded bubble. The dyad symmetry region unwinds to form a broad single-stranded bubble containing hairpins in the 65-bp dyad sequence. We propose that the intrinsic ease of unwinding the dyad symmetry region, the actual origin of DNA replication, is an important component in the mechanism of initiation.
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PMID:Easily unwound DNA sequences and hairpin structures in the Epstein-Barr virus origin of plasmid replication. 838 73

Thermal stress induces expression of a family of heat shock proteins which may regulate the synthesis of various cellular genes. We investigated the effect of heat shock on polyadenylation in Epstein-Barr Virus (EBV) negative and EBV transformed human Burkitt's lymphoma (BL) B-cell lines. Incubation of the BL B-cell line P3HR-1, carrying the defective EBV genome [EBV nuclear antigen-2 gene deletion] at 46 degrees C for 15 min increased nuclear poly(A) polymerase (PAP) activity. Thereafter, enzymatic activity declined and at 60 min it was reduced to about 50% of that observed in cells incubated at 37 degrees C. In contrast, no significant increase in PAP activity was observed at 15 min or thereafter in an EBV- BL cell line, ST-486, in response to elevated temperature. Furthermore, no heat shock mediated change in nuclear poly(A)-specific endonuclease activity was observed in either P3HR-1 or ST-486 cells suggesting a specific effect on PAP activity. However, thermal stress dependent increase in c-myc expression was detected only in P3HR-I cells. These results suggest an association between EBV transformation and enhanced expression of c-myc and PAP activity. To further determine the role of EBV, and EBV- BL cell line, BL-30, and BL-30 cells infected in vitro with a wild type strain of EBV, BL-30/B95-8, were investigated. BL-30/B-95-8, unlike the parental BL-30 cells, exhibited c-myc and PAP gene upregulation at 15 min but were downregulated at 60 min following exposure of cells to elevated temperatures. These results suggest that infection of human B-cells with EBV is associated with their ability to respond to thermal stress by increased PAP activity which may stabilize mRNA through enhanced polyadenylation.
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PMID:Differential effect of heat shock on RNA metabolism in human Burkitt's lymphoma B-cell lines. 855


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