Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Superinfection of Raji cells with Epstein-Barr virus induced a new thymidine kinase that was distinguishable from both adult and fetal kinases of the host cell by discontinuous electrophoresis on polyacrylamide gels and glycerol gradients.
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PMID:Epstein-Barr virus-associated thymidine kinase. 20 28

Association of herpes simplex virus (HSV)-related antigens with chromosomes was demonstrated in human and mouse cells biochemically transformed by HSV that had been irradiated with ultraviolet light. This was accomplished by using peroxidase-anti-peroxidase immunological staining with rabbit antisera that had high neutralizing titers against both HSV-specific thymidine kinase activity and virus infectivity. Antisera-against HSV did not react with chromosomes of uninfected cells nor did normal sera react with any of the constitutents of biochemically transformed cells. Methanol/acetic acid treatment of biochemically transformed cells eliminated their nuclear staining for HSV-related antigens. In vitro binding of HSV-related antigens to chromosomes was demonstrated by incubating soluble antigens from high salt extracts of HSV-infected cells with methanol/acetic acid-fixed chromosomes of biochemically transformed or uninfected cells, followed by exposure to antiserum against HSV and peroxidase-anti-peroxidase staining. There was no staining when soluble extracts from uninfected cells were substituted for those from HSV-infected cells. The results show that cells biochemically transformed and lytically infected by HSV, respectively, contain antigens, which like the Epstein-Barr virus-associated nuclear antigen (EBNA), bind to chromosomes in vivo and in vitro.
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PMID:Binding to chromosomes of herpes simplex-related antigens in biochemically transformed cells. 21 Apr 57

We previously located two 12-O-tetradecanoylphorbol-13-acetate (TPA)-responsive enhancers, MSTRE-I and MSTRE-II, in the upstream sequence of the MS gene of Epstein-Barr virus (Liu, Q., and Summers, W.C. (1989) J. Virol. 63, 5062-5068). The core sequence of the MSTRE-I enhancer is now determined to be between -718 and -708 of the upstream sequence of the MS gene. The activity of the enhancer is also sensitive to its immediate surrounding sequence on either side. A single copy of a 30-base pair (bp) fragment containing the MSTRE-I sequence was able to confer TPA responsiveness upon the MS promoter even in the absence of an AP-1 binding site. Multiple tandem copies of this 30-bp fragment, regardless of their relative orientations to each other, could function synergistically to enhance the MS promoter activity. At least two copies of the 30-bp fragment were required to bestow TPA induction upon the thymidine kinase gene promoter of herpes simplex virus type 1. The MSTRE-I sequence could also be bound by a Fos-GCN4 chimeric protein but with an affinity much lower than that between the chimeric protein and the AP-1 binding site. This MSTRE-I region has strong homology to one of the TPA-responsive elements (the ZII domain) in the upstream sequence of the EBV BZLF1 gene. In addition, a putative negative regulatory region or silencer was found immediately downstream of the MSTRE-I enhancer. This potential silencer region contains a 14-bp sequence that is homologous to the silencer consensus sequence of the BZLF1 gene. Therefore, the regulation of the MS gene may share the same pathway with the immediate early gene BZLF1.
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PMID:Identification of the 12-O-tetradecanoylphorbol-13-acetate-responsive enhancer of the MS gene of the Epstein-Barr virus. 131 8

A clone of the Epstein-Barr virus (EBV) thymidine kinase (TK) gene was derived from a cDNA library of P3HR1 cells. The gene product was expressed as a fusion protein in a procaryotic system by using T7 RNA polymerase. The recombinant TK showed a molecular mass of 67 kDa and was biologically active. Antiserum raised in mice immunized with partially purified TK recognized an antigen present in EBV-superinfected Raji cells using an indirect immunofluorescence assay.
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PMID:Cloning and expression of a cDNA encoding the Epstein-Barr virus thymidine kinase gene. 133 Nov 57

We used a shuttle vector based on the Epstein-Barr virus origin of plasmid replication (oriP) to determine the types of mutations induced by depurination in human cells. Plasmid DNA was incubated at pH 2 at 40 degrees C for various times to induce up to 20 apurinic (AP) sites per 9.7-kb plasmid and electroporated into lymphoblastoid cells derived from either a normal individual or an ataxia telangiectasia patient. After replication of the vector in the human cells, plasmid DNA was isolated and analyzed for mutations induced in the plasmid-encoded herpes simplex virus type 1-thymidine kinase gene. Both the frequencies and types of mutations induced by depurination were essentially identical for normal and ataxia telangiectasia cells. The mutant frequency at 20 AP sites/plasmid was 10-fold to 13-fold greater than that observed for untreated DNA. Deletion and frameshift events accounted for 46-55% of the mutants induced by depurination. The induced deletions were relatively small (median size, 100-150 bp) and characterized by short (1-5 bp) regions of sequence homology at the endpoints. These mutations and the frameshifts, a majority of which occurred in runs of identical nucleotides, are consistent with a model involving AP-site-induced template dislocation during DNA synthesis. A broad spectrum of base-substitution mutations, which accounted for 19-36% of the induced mutants, was observed. The apparent preference for insertion opposite AP sites in human cells was G (43-55%) greater than A approximately C (18-21%) greater than T (9-14%). Our results in human cells contrast markedly with those published previously for the mutational specificity of AP sites in Escherichia coli, in which a large majority of the mutants resulted from insertion of an A opposite the abasic site.
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PMID:Mutagenesis by apurinic sites in normal and ataxia telangiectasia human lymphoblastoid cells. 150 43

Glucocorticoids induce the expression of Epstein-Barr virus early antigens in latently infected Daudi cells. By sequence analysis, we found that fragment C of the BamHI digested Epstein-Barr virus B95-8 genome contains a region with a large degree of homology to the glucocorticoid responsive element of known glucocorticoid-regulated genes. By transfection experiments in Daudi and HeLa cells, different lengths of this region, cloned in front of the bacterial chloramphenicol acetyl transferase linked to the Herpes Simplex virus thymidine kinase promoter (pBLCAT.2), were assayed for their responsiveness to dexamethasone; our results led us to the conclusion that the hormonal effect observed was mediated by a minimal sequence of 15 base pairs presenting 85% homology with the consensus glucocorticoid responsive element sequence.
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PMID:Evidence for a functional glucocorticoid responsive element in the Epstein-Barr virus genome. 164 55

Epstein-Barr virus (EBV) nuclear protein 2 (EBNA-2) is essential for B-lymphocyte growth transformation. EBNA-2 upregulates mRNAs encoding CD23, a B-lymphocyte surface protein closely associated with EBV-induced growth transformation. To further investigate this EBNA-2 effect, we searched in the genomic DNA spanning the type a and type b CD23 mRNA start sites for a cis-acting fragment that would render a promoter transactivatable by EBNA-2. An 800-bp CD23 DNA fragment (-335 to +465 relative to the type a CD23 mRNA start site) conferred EBNA-2 responsiveness to the herpes simplex virus thymidine kinase (TK) promoter when transfected into EBV-negative B-lymphoma cells. Deletional analysis identified a -275/-89 subfragment that was EBNA-2 responsive when cloned in either orientation and at variable distances upstream of the heterologous promoter. EBNA-2 and the cis-acting CD23 element increased TK-promoted mRNA and did not alter the herpes simplex virus TK promoter transcription start site. As expected, a type a CD23 promoter (-335/+80) which contained the EBNA-2-responsive element was transactivated by EBNA-2. As in EBV infection and stable EBNA-2 transfection, the CD23 DNA element in cis with heterologous or homologous promoters was less responsive to type 2 than to type 1 EBNA-2, whereas the EBNA-2-responsive DNA fragment from the EBV latent membrane protein 1 promoter was more responsive to the type 2 EBNA-2. These experiments delineate a 186-bp, EBNA-2-responsive cell DNA fragment and provide firm evidence that EBNA-2 transactivates transcription of cell genes. The greater type 1 versus type 2 EBNA-2 responsiveness of the CD23 promoter and the lack of a similar effect on the latent membrane protein 1 promoter is consistent with the hypothesis that greater cell gene transactivation by type 1 EBNA-2 is the basis for the more efficient growth-transforming properties of type 1 EBV.
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PMID:Epstein-Barr virus nuclear protein 2 transactivates a cis-acting CD23 DNA element. 164 18

We have studied the relative rate of transcription across the Epstein-Barr virus genome in the Burkitt's lymphoma cell line Raji by nuclear run-on analysis during latency and after induction of an abortive lytic cycle with 12-0-tetradecanoylphorbol 13-acetate (TPA) and 5-iodo-2'-deoxyuridine (IUdR). During latency the entire, or almost the entire, viral genome was found to be transcriptionally active to a low or intermediate extent, with some variation in activity along the genome. The fragment with the highest transcriptional activity was EcoRI J, which contains the genes encoding the small nuclear RNAs EBER1 and -2, transcribed predominantly by RNA polymerase III. An intermediate level of transcription was observed between positions 10 and 138 (kb), with areas of slightly higher activity on the large internal repeats and the left duplicated region (DL). The remaining part of the viral genome, between position 138 and the termini, and the termini and position 10 (kb) (with the exception of the EcoRI J fragment), showed very little transcriptional activity, except for the intermediately active regions carrying the righthand oriLyt (DR) and the terminal repeats. Upon induction of the viral genome with TPA and IUdR, the viral genome was transcriptionally active at a rate at least tenfold that seen during latency. Polymerases were not equally distributed along the genome after induction; the highest density was found in regions 48 to 58 kb, 82 to 84 kb, 102 to 104 kb, 118 to 122 kb and 142 to 145 kb of the viral genome. High transcriptional activity correlated with distinct transcription units in some cases, i.e. BamHI H1LF1 (DL), BamHI MLF1, BamHI ZLF1/BamHI RLF1 and BamHI X (thymidine kinase), but not in others (BamHI H2). Besides initiation of transcription, other regulatory processes such as stabilization and processing of primary transcripts may also contribute to regulation of virus gene expression. Addition of cycloheximide completely abolished the transcriptional activation of the genome mediated by TPA and IUdR.
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PMID:Transcriptional activity across the Epstein-Barr virus genome in Raji cells during latency and after induction of an abortive lytic cycle. 165 54

To delineate the cis-acting element through which EBNA-2 transactivates latent membrane protein 1 (LMP1), we assayed the effect of EBNA-2 on the activity of LMP1 promoter upstream deletion mutants in the context of the LMP1 or heterologous promoters controlling chloramphenicol acetyltransferase (CAT) reporter gene expression in Epstein-Barr virus-negative Burkitt lymphoma cells. Assays of progressive 5' deletions of the LMP1 promoter revealed low constitutive and at least eightfold EBNA-2-stimulated activity from -512 to +40 (-512/+40), -334/+40, and -234/+40 LMP1CAT plasmids. More extensive 5'-deleted -205/+40, -155/+40, and -147/+40 LMP1CAT plasmids also had low constitutive activity but were not EBNA-2 responsive. The most 5'-deleted -55/+40 LMP1CAT plasmid had moderate constitutive activity and was not EBNA-2 inducible. Either orientation of the -334/+40 LMP1 sequence conferred EBNA-2 responsiveness when positioned upstream of an enhancerless simian virus 40 or herpes simplex virus thymidine kinase (TK) promoter. EBNA-2 and the cis-acting LMP1 DNA were both required to increase TK promoter-initiated mRNA, indicating that the EBNA-2 effect is at the transcriptional level. Further deletion analysis of the EBNA-2-responsive cis-acting element defined a -234/-92 LMP1 DNA fragment which conveyed EBNA-2 responsiveness to the herpes simplex virus TK promoter. The 5' 30 bp between -234 and -205 were essential for EBNA-2 responsiveness. Thus, these experiments define a 142-bp cis-acting element which is sufficient for conveying EBNA-2 responsiveness and an essential 30-bp component of that element. The role of this element in LMP1 and LMP2B expression and its possible role in LMP2A expression are discussed.
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PMID:Delineation of the cis-acting element mediating EBNA-2 transactivation of latent infection membrane protein expression. 165 73

The immune response of patients with nasopharyngeal carcinoma to Epstein-Barr virus (EBV) antigens is diagnostic of the tumour. Existing tests use EBV antigens produced in EBV-infected lymphoblastoid cells, but the virus replicates poorly in these cells. Serum samples from 18 patients diagnosed as having nasopharyngeal carcinoma were screened by western blot analysis, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence tests for antibodies to the EBV-coded alkaline deoxyribonuclease (DNase), thymidine kinase, and membrane antigen (gp340/220) produced in recombinant baculovirus or bovine papillomavirus systems. Each protein was a useful diagnostic marker for nasopharyngeal carcinoma, although in the gp340/220 ELISAs there was substantial overlap for both IgG and IgA antibodies between serum samples from nasopharyngeal carcinoma patients and those from healthy donors seropositive for EBV. The EBV thymidine kinase was the most sensitive predictor of nasopharyngeal carcinoma; all such samples showed both IgG and IgA antibody responses to this protein and all gave clearly distinct titres from those of the EBV-seropositive donors in the IgA test. Each of the recombinant systems described is suitable for use in large-scale screening programmes for the early diagnosis of nasopharyngeal carcinoma.
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PMID:Diagnosis of nasopharyngeal carcinoma by means of recombinant Epstein-Barr virus proteins. 167 75


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