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:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CD8+ cytotoxic T (Tc) lymphocytes mediate recovery from vaccinia virus (VV) infection. In mice, anti-VV Tc cells are detectable on or after day 3 after infection, and cytolytic activity peaks between days 5 and 6. A rVV encoding murine IL-2, VV-hemagglutinin (HA)-IL-2, was cleared more rapidly, compared with a control rVV, VV-HA-thymidine kinase (TK), from tissues of infected euthymic normal mice. The mechanism of VV-HA-IL-2 clearance was operative early in infection and correlated with an elevated NK cell response, before the induction of anti-VV Tc cell response. We have investigated the roles of NK cells, T cells, and IFN-gamma in the rapid clearance of VV-HA-IL-2, by using specific mAb. Depletion of NK cells with mAb significantly enhanced VV-HA-IL-2 but not VV-HA-TK titers 3 days after infection. NK cells alone could not account for rapid viral clearance, because VV-HA-IL-2 titers in NK cell-depleted mice were not comparable to VV-HA-TK titers. Treatment with a mAb to IFN-gamma completely abrogated the IL-2-induced mechanism(s) of VV-HA-IL-2 clearance, and titers of the IL-2-encoding virus were comparable to control virus titers. In addition, the elimination of CD4+ but not CD8+ T cells resulted in significant increases in VV-HA-IL-2 titers.
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PMID:Immunobiology of infection with recombinant vaccinia virus encoding murine IL-2. Mechanisms of rapid viral clearance in immunocompetent mice. 168 75

The interferon (IFN)-gamma-mediated induction of indoleamine 2,3-dioxygenase (IDO) enzyme, which converts tryptophan into N-formylkynurenine, has been implicated in the inhibition of intracellular pathogens, e.g. Toxoplasma gondii and Chlamydia psittaci, and in the antiproliferative effect of IFN-gamma on tumor cells. The IDO activity is induced strongly in many cell types by IFN-gamma but rather poorly by IFN-alpha or -beta. A genomic DNA clone containing part of the transcribed region of the IDO gene and approximately 13 kilobases (kb) of the 5'-upstream DNA sequence was isolated and analyzed. An approximately 1.4-kb fragment of this clone, containing 329 nucleotides of the transcribed sequence and approximately 1.1 kb of the 5'-upstream sequence, when ligated to chloramphenicol acetyltransferase (CAT) structural gene made its expression inducible by IFN-gamma, but this construct responded poorly, if at all, to IFN-alpha 2. Deletion constructs derived from this plasmid narrowed down the IFN-gamma-responsive region to a 151-nucleotide segment (-495/-344) which also contained a 14-nucleotide sequence (GGTTTCAGTTTTCC) highly homologous to the IFN(alpha)-stimulated response element (ISRE) that has been found so far in all cellular genes inducible with IFN-alpha or -beta. Expression of CAT activity was stimulated by IFN-gamma more effectively than by IFN-alpha 2 when a 155-nucleotide fragment (-495/-340) containing the 151-nucleotide segment required for IFN-gamma response was inserted before herpes simplex virus thymidine kinase promoter linked to CAT structural gene. The results indicate that despite the presence of an ISRE, the control region of the IDO gene can distinguish between IFN-gamma and IFN-alpha. This may account for the differential activation of IDO gene expression by IFN-gamma as against IFN-alpha or -beta in intact cells, and suggests that the response of ISRE to IFN-alpha or -beta may be governed by other features in the upstream control region of this gene.
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PMID:Regulation of indoleamine 2,3-dioxygenase gene expression in human fibroblasts by interferon-gamma. Upstream control region discriminates between interferon-gamma and interferon-alpha. 217 56

Cotransformation with a plasmid containing a thymidine kinase gene (pTK2) and a plasmid encoding human IFN-gamma (pTG11) has been used to establish murine L cell lines expressing human IFN-gamma. The HuIFN-gamma gene was present in 30% of the tk+ cell lines and some of these secreted low levels of IFN into the culture medium. Two of the clones obtained after transformation were selected for detailed analysis. Clone 1-12 constitutively secreted very low levels of HuIFN-gamma in the culture medium. This antiviral activity was characterized by its species specificity and antigenicity as authentic human IFN-gamma In contrast, clone 3-47 produced a HuIFN-gamma activity which could only be detected intracellularly. This clone was resistant to infection both by Vesicular stomatitis (VSV) and Mengo viruses and contained increased levels of enzymes known to be induced by interferon. Our results suggest that clone 3-47 produces a non-secreted HuIFN-gamma like molecule which is able to trigger an antiviral state in the murine cell independent of the interaction with a specific IFN-gamma surface receptor.
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PMID:Expression of extracellular and intracellular human IFN-gamma in mouse L cells transformed with the human IFN-gamma cDNA gene. 242 24

The induction of class II antigen on primary macrophages and on several macrophage cell lines has been demonstrated after exposure to IFN-gamma. The murine macrophage cell line PU5 (H-2d haplotype) does not express class II antigen constitutively and only trace levels are detected after induction with IFN-gamma. In an attempt to understand the nature of the defect in PU5, stable macrophage hybrids were derived by fusing a thymidine kinase-negative variant of PU5 with thioglycollate elicited peritoneal macrophages from CBA/J mice (H-2k haplotype). Hybrid clones isolated after HAT selection had approximately 35% more DNA than the PU5 parent suggesting that chromosomal loss had occurred post-fusion. While none of the hybrids expressed class II antigens of the k haplotype, constitutive expression of class II antigens of the d haplotype was detected by both micro-ELISA and by flow cytometry. Incubation of these hybrids with IFN-gamma resulted in a further increase in class II expression. Co-ordinate reactivation of both I-A and I-E antigens was observed in the PU5-macrophage hybrids. In contrast, although the IFN-gamma receptor on PU5 and the macrophage hybrids was indistinguishable by Scatchard analysis, neither intracellular class II antigen nor transcription of class II mRNA was detected in IFN-gamma-treated PU5. Reactivation was dependent on the PU5 fusion partner and was not related to a general post-fusion event as hybrids formed between PU5 and the murine fibroblast line A9 did not express class II antigen constitutively or after IFN-gamma induction.
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PMID:Reactivation of class II antigen expression in murine macrophage hybrids. 296 70

Rapamycin (RAP) disrupts signaling events implicated in cytokine-dependent proliferation of lymphocytes and other cells. This action is known to involve the formation of molecular complexes between the drug and intracellular binding proteins, termed FKBPs. However, the biochemical target(s) for the effector RAP-FKBP complexes remain uncharacterized. As an approach to explore the mechanism of action of RAP, we have isolated three independent sets of somatic mutants of the YAC-1 murine T cell line with markedly reduced sensitivity to the drug's inhibitory effects on proliferation and on IL-1-induced IFN-gamma production. These mutants were still fully sensitive to FK-506, an immunosuppressant structurally related to RAP whose mode of action also involves an interaction with FKBPs. Furthermore, the 12-kDa FKBP, FKBP12, was detectable in immunoblots from cytosolic extracts and eluates from RAP-affinity matrix in the mutants as in wild-type cells, suggesting that the resistance to RAP in the mutants is not due to a lack of FKBP12 expression. Cell fusion experiments were conducted to further define the nature of the alterations imparting RAP resistance in these mutants. Clones deficient in either thymidine kinase or hypoxanthine-guanine phosphoribosyltransferase, suitable as fusion partners for aminopterin-based selection of hybrids were generated from the wild-type or mutant lines. In most instances, the hybrids derived from the fusion between RAP-sensitive clones and RAP-resistant clones exhibited a RAP-resistant phenotype. Similar results were obtained with hybrids between RAP-resistant YAC-1 clones and the RAP-sensitive EL-4 cell line. Therefore, the mutations that confer resistance to RAP in the present system are dominant. Altogether, our observations are consistent with a model where pharmacologically relevant targets for the RAP-FKBP complex, rather than FKBP, might be altered in the mutants such that the inactivation of these targets by the effector complex is prevented.
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PMID:Dominant mutations confer resistance to the immunosuppressant, rapamycin, in variants of a T cell lymphoma. 753 11

Interferon (IFN)-gamma-induced expression of indoleamine 2,3-dioxygenase (IDO) gene is implicated in the antimicrobial and antiproliferative effects of IFN-gamma in cell cultures. Earlier studies identified a 96 base pair (bp) regulatory region upstream of the IDO gene that conferred IFN-gamma response to the chloroamphenicol acetyltransferase (CAT) gene linked to herpesvirus thymidine kinase promoter. The IFN-gamma-responsive region was further narrowed to a 67 bp fragment by 3' deletion. This 67 bp fragment contains several sequence elements of potential interest, including a 14 bp sequence homologous to the ISRE sequence found in IFN-alpha-inducible genes and two palindromic sequences (PE I and PE II) homologous to the GAS sequence identified in IFN-gamma-inducible genes. Site-directed mutagenesis studies showed that IFN-gamma-induced expression of IDO-CAT constructs involved cooperation between two elements: the ISRE homolog and the PE II (but not PE I). Either element alone with its flanking sequence was inadequate in conferring an IFN-gamma response to CAT reporter gene. Two IFN-gamma-regulated protein factors interacting with these two elements were identified. The factor binding to the ISRE region was induced with a slower kinetics, required new protein synthesis, and reacted with antibodies to IRF-1. The factor interacting with the PE II region appeared rapidly after treatment with IFN-gamma independently of new protein synthesis, and its binding to DNA probe was blocked by antibodies to p91 factor, reported to bind to GAS element.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Involvement of two regulatory elements in interferon-gamma-regulated expression of human indoleamine 2,3-dioxygenase gene. 755 21

We have previously demonstrated that genetically modified syngeneic murine tumor cells (KBALB) expressing the herpes simplex virus thymidine kinase gene (HSV-STK) can kill nearby unmodified tumor cells in the presence of ganciclovir (GCV). The killing was mediated by a 'bystander effect' as evidenced by the prolonged animal survival when syngeneic HSV-TK gene-modified tumor cells were inoculated into mice with an intraperitoneal tumor. In this study we investigated whether irradiated xenogeneic HSV-TK gene-modified tumor cells, a human colon carcinoma cell line (HCT) transfected with the HSV-TK gene, can mediate the 'bystander effect' when used in vitro and in vivo. In vitro experiments indicate that irradiated HSV-TK gene-modified xenogeneic cells (HCT) can mediate a bystander effect on the adjacent cells when the tumor population consisted of as few as 10% of the HSV-TK expressing HCT tumor cells. In vivo, animal survival experiments demonstrate that the xenogeneic gene-modified tumor cells could generate the 'bystander effect' in mice with intraperitoneal tumors as evidenced by prolonged animal survival. In addition, histologic examination of the tumors from experimental animals showed extensive tumor necrosis 3 days post HSV-TK/GCV treatment in comparison to control animals. To evaluate the cause of necrosis in vivo, we assayed for cytokines, which may be involved in mediating this process, by performing RT-PCR and immunohistochemistry on tumor RNA and tumor cells, respectively. Production of IL-1 alpha and IL-6 mRNA within the experimental tumors was observed by RT-PCR. However, mRNA expression for other cytokines including IFN-gamma, IL-2 and IL-4 was not present. Immunohistochemical analysis for IL-1 alpha protein showed reactivity within the infiltrating mononuclear cells indicating the release of this soluble factor. These results indicate that the bystander effect can be generated using irradiated xenogeneic cells both, in vitro and in vivo. Furthermore, this process is mediated by the release of cytokines such as IL-1 alpha, IL-6 which enhances the bystander effect in vivo by immunostimulation.
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PMID:The role of cytokines in mediating the bystander effect using HSV-TK xenogeneic cells. 760 May 27

To understand the mechanisms involved in dsRNA-induced gene expression, we analyzed the poly(I/C)-induced transcription of the IFN-inducible chemokine gene IP-10 using the GRE cell line in which type I IFN genes have been deleted. Accumulation of IP-10 mRNA in GRE cells was more strongly stimulated by treatment with dsRNA than by IFN-alpha or IFN-gamma and was independent of protein synthesis. This same pattern of response was produced when GRE cells were transiently transfected with a plasmid containing 243 bases of sequence from the promoter of the murine IP-10 gene linked to the chloramphenicol acetyltransferase reporter gene. Deletion- and site-specific mutagenesis of the 243 base pair fragment indicated that an ISRE located between residues -204 and -228 was a primary target site for the action of dsRNA on this promoter. This was confirmed by results showing that two copies of this ISRE tandemly arrayed in front of the thymidine kinase promoter were able to mediate reporter gene transcription in dsRNA-stimulated cells. At least one of the two NF kappa B binding sites present in the 243 base pair IP-10 promoter is also necessary for response to dsRNA; mutation of both sites eliminates promoter activity. Thus the ISRE and one NF kappa B site cooperate to produce transcriptional response to dsRNA.
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PMID:Interferon-stimulated response element and NF kappa B sites cooperate to regulate double-stranded RNA-induced transcription of the IP-10 gene. 789 55

Previous analysis of the human interferon-gamma (IFN-gamma promoter indicated that the region of DNA from -251 to -215 (designated here as BE (binding element)) possessed silencer activity, as deletion of this region caused an increase in promoter activity. Based on this finding, we have conducted a series of experiments to characterize BE function and analyze the binding proteins which interact with this region. Transient transfection assays in the Jurkat T cell line revealed that the BE region possesses silencer activity, which is orientation-dependent when reinserted 5' to the IFN-gamma core promoter. However, when the BE region was inserted in front of a heterologous promoter (thymidine kinase (TK)), a mild enhancer activity was observed. Utilizing the electrophoretic mobility shift assay, we have identified two major DNA-protein complexes (designated as S and E complexes) which interact with this region. Mutational analysis indicated that the silencer activity observed with the IFN-gamma promoter correlated with the S complex and the enhancer activity correlated with the E complex. Preliminary characterization of these two DNA-protein complexes has demonstrated the presence of multiple proteins in each complex. We have found that the S protein complex has a recognition sequence similar to the nuclear factor AP2, and we have identified the nuclear factor Yin-Yang 1 (YY1) as one of the proteins in the E complex.
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PMID:Characterization of a silencer regulatory element in the human interferon-gamma promoter. 792 77

To define the molecular mechanisms involved in the action of gamma interferon (IFN-gamma), we have analyzed the transcriptional regulation of the mig (monokine induced by gamma interferon) gene, a member of the platelet factor 4-interleukin-8 cytokine family that is expressed in murine macrophages specifically in response to IFN-gamma. Analysis of mig/CAT chimeric constructs transiently transfected into the RAW 264.7 mouse monocytic cell line revealed a unique IFN-gamma-responsive element (gamma RE-1). The sequence of this cis regulatory element defined by deletion analysis contains an imperfect inverted repeat extending 27 bp. Examination of mig/CAT constructs with mutations in gamma RE-1 revealed that the palindromic positions in the element were essential for activity. Consistent with its function as an enhancer, a single copy of gamma RE-1 conferred IFN-gamma inducibility to a heterologous (herpes simplex virus thymidine kinase) promoter. Exonuclease III protection assays demonstrated symmetrical protection of a mig promoter fragment centered about the gamma RE-1 palindromic sequence. Using the gel electrophoretic mobility shift assay, we identified a factor (gamma RF-1) present in nuclear extracts prepared from IFN-gamma-stimulated RAW 264.7 cells which binds to gamma RE-1. The activation of gamma RF-1 occurred rapidly (within 1 min) in response to IFN-gamma and was independent of protein synthesis. Similar to the expression of mig mRNA, the formation of gamma RF-1 was selectively induced by IFN-gamma and not IFN-alpha. The regulation of gene expression through gamma RF-1 and gamma RE-1 may explain the preferential activation of a subset of interferon-inducible genes by IFN-gamma.
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PMID:A unique palindromic element mediates gamma interferon induction of mig gene expression. 828 31


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