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)

The present studies have examined the effects of ionizing radiation on control of the early growth response 1 (EGR1) gene. Exposure of human HL-525 cells to x-rays was associated with increases in EGR1 mRNA levels. Nuclear run-on assays showed that this effect is related at least in part to activation of EGR1 gene transcription. Sequences responsive to ionizing radiation-induced signals were determined by deletion analysis of the EGR1 promoter. The results demonstrate that x-ray inducibility of the EGR1 gene is conferred by a region containing six serum response or CC(A+T-rich)6GG (CArG) motifs. Further analysis confirmed that the region encompassing the three distal or upstream CArG elements is functional in the x-ray response. Moreover, this region conferred x-ray inducibility to a minimal thymidine kinase gene promoter. Taken together, these results indicate that ionizing radiation induces EGR1 transcription through CArG elements.
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PMID:Ionizing radiation activates transcription of the EGR1 gene via CArG elements. 133 31

The present work has examined the effects of okadaic acid, an inhibitor of serine/threonine protein phosphatase, PP-1 and PP-2A, on the regulation of EGR-1 gene expression in normal peripheral blood T- and Jurkat cells. The results demonstrate that okadaic acid treatment is associated with a transient induction of EGR-1 gene expression which was detectable by 30 min to 1 h and peaked at 3-6 h. EGR-1 mRNA was superinduced in cells treated with both okadaic acid and the protein synthesis inhibitor cycloheximide. The half-life of EGR-1 mRNA was similar in both control and okadaic acid-treated cells. In contrast, treatment with both okadaic acid and cycloheximide prolonged the half-life of EGR-1 transcripts. Nuclear run-on assays demonstrated that induction of EGR-1 gene expression by okadaic acid is controlled at least in part by a transcriptional mechanism. Transient expression assays with EGR-1 promotor fragments linked to the chloramphenicol acetyltransferase gene demonstrate that okadaic acid-induced EGR-1 transcription is conferred by the 5' most distal CArG box, CC (AT)6GG, in the EGR-1 promoter. Moreover, chloramphenicol acetyltransferase activity was induced by okadaic acid when the 5' most distal CArG element was linked to the heterologous herpes simplex virus thymidine kinase promoter, and not induced with a similar heterologous construct containing a mutated CArG sequence. These studies demonstrate that okadaic acid regulates EGR-1 gene expression at the transcriptional level via the CArG element and suggest that PP-1 and PP-2A play a role in T-cell activation.
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PMID:Involvement of serum response element in okadaic acid-induced EGR-1 transcription in human T-cells. 817 32

The early growth response 1 (EGR-1) gene is induced after mitogenic stimulation of diverse cell types. The present work has examined the effects of okadaic acid, an inhibitor of protein phosphatases 1 and 2A, on EGR-1 expression during monocytic differentiation of U-937 myeloid leukemia cells. Treatment of U-937 cells with okadaic acid was associated with transient increases in EGR-1 mRNA levels. These increases were maximal at 6 h and occurred in the absence of de novo protein synthesis. Nuclear run-on assays demonstrated that although EGR-1 transcription is detectable in untreated U-937 cells, this rate is increased 6-fold by okadaic acid. Sequences responsive to okadaic acid-induced signals were determined by deletion analysis of the EGR-1 promoter. The results demonstrate that okadaic acid-induced EGR-1 transcription is dependent on the presence of CC (A/T)6 GG (CArG) motifs. The EGR-1 promoter contains six CArG boxes. However, only the 5'-most distal (first) CArG sequence conferred okadaic acid inducibility. A 40-base pair oligomer corresponding to the first CArG element also conferred okadaic acid inducibility of the minimal thymidine kinase gene promoter. In contrast, there was no inducibility using a similar oligomer containing a mutated CArG box. Finally, binding of nuclear proteins to the first CArG sequence was similar for control and okadaic acid-treated cells. Taken together, these results suggest that okadaic acid activates EGR-1 transcription and that this event is mediated at least in part by a single CArG element.
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PMID:Transcriptional regulation of the early growth response 1 gene in human myeloid leukemia cells by okadaic acid. 838 Oct 16

The expression of NGFIA (also known as egr1, zif268, TIS8, krox24, and d2) is rapidly and transiently increased by nerve growth factor (NGF) in PC12 cells. The 5'-region of this gene includes four serum response elements (SREs), a cAMP-like response element, an AP1-like response element, and an SP1-binding site. From deletion analysis of chloramphenicol acetyltransferase reporter constructs, we have established that the first 106 basepairs 5' of the transcriptional start site are sufficient for induction of NGFIA by NGF in PC12 cells; deletion beyond this point results in dramatically reduced induction of the gene. Using defined mutations in the NGFIA promoter and NGFIA-thymidine kinase hybrid promoters, we have defined three elements (SRE1, SRE2, and AP1-like) in the first 106 basepairs of upstream DNA, each of which contributes to induction of NGFIA by NGF. Cooperation by two of these elements (i.e. the two SREs or one SRE and the AP1-like element) is sufficient to confer transcriptional induction by NGF, but the combination of all three elements increased induction by NGF more effectively than a pair of elements. This suggests that the response of NGFIA to NGF is mediated by a cis-acting sequence that is composed of at least three distinct elements. An oligonucleotide composed of SRE1 and SRE2 that can confer the ability for NGF induction to heterologous promoter constructs complexes with proteins in PC12 cell nuclear extracts, but the protein-DNA complexes do not appear to be altered by NGF treatment, as measured by DNA mobility shift assays. We have also established that the regulatory region of NGFIA that mediates NGF induction also mediates the induction by serum and phorbol 12-myristate 13-acetate, suggesting that multiple signal transduction pathways must converge on these sequences to regulate the expression of this gene.
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PMID:Nerve growth factor induces transcription of NGFIA through complex regulatory elements that are also sensitive to serum and phorbol 12-myristate 13-acetate. 848 78

Exposure of cells to ionising radiation results in the activation of specific transcriptional control (CArG) elements within the early growth response 1 (Egr1) gene promoter, leading to increased gene expression. As part of a study investigating the potential use of these elements in radiation-controlled gene therapy vectors, we have incorporated their sequences into a synthetic gene promoter and assayed for the ability to induce expression of a downstream reporter gene following irradiation. In vector-transfected MCF-7 breast adenocarcinoma cells, the synthetic promoter was more effective than the wild-type Egr1 counterpart in up-regulating expression of the reporter gene after exposure to a single 5 Gy dose, and equally effective as the wild-type in U87-MG glioma cells. The level of gene expression achieved using the synthetic promoter was dependent on the inducing radiation dose for both U87-MG and MCF-7 cells, being maximal at 3 Gy and decreasing at 5 and 10 Gy. Furthermore, induction could be repeated by additional radiation treatments. The latter indicates that up-regulation should be additive during fractionated radiotherapy schedules. To demonstrate the potential clinical benefit of such an approach, the synthetic promoters were also shown to drive expression of the herpes simplex virus thymidine kinase gene, leading to enhanced cell killing in the presence of the prodrug ganciclovir (GCV) when compared with cells treated with radiation alone. Our results demonstrate that the synthetic promoter is responsive to low doses of ionising radiation and therefore isolated CArG elements function as radiation-mediated transcriptional enhancers outside their normal sequence context. The continued development and optimisation of such radiation-responsive synthetic promoters is expected to make a valuable contribution to the development of future radiation-responsive vectors for cancer gene therapy.
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PMID:Development of synthetic promoters for radiation-mediated gene therapy. 1108 80

A novel therapy for Epstein-Barr virus (EBV)-positive tumors involves the intentional induction of the lytic form of EBV infection combined with ganciclovir (GCV) treatment. Virally encoded kinases (thymidine kinase and BGLF4) which are expressed only during the lytic form of infection convert GCV (a nucleoside analogue) into its active, cytotoxic form. However, tightly latent EBV infection in B cells has made it difficult to identify drugs that can be used clinically to induce lytic viral infection in B-cell lymphomas. Here we demonstrate that gemcitabine and doxorubicin (but not 5-azacytidine, cis-platinum, or 5-fluorouracil) induce lytic EBV infection in EBV-transformed B cells in vitro and in vivo. Gemcitabine and doxorubicin both activated transcription from the promoters of the two viral immediate-early genes, BZLF1 and BRLF1, in EBV-negative B cells. This effect required the EGR-1 motif in the BRLF1 promoter and the CRE (ZII) and MEF-2D (ZI) binding sites in the BZLF1 promoter. GCV enhanced cell killing by gemcitabine or doxorubicin in lymphoblastoid cells transformed with wild-type EBV, but not in lymphoblastoid cells transformed by a mutant virus (with a deletion in the BZLF1 immediate-early gene) that is unable to enter the lytic form of infection. Most importantly, the combination of gemcitabine or doxorubicin and GCV was significantly more effective for the inhibition of EBV-driven lymphoproliferative disease in SCID mice than chemotherapy alone. In contrast, the combination of zidovudine and gemcitabine was no more effective than gemcitabine alone. These results suggest that the addition of GCV to either gemcitabine- or doxorubicin-containing chemotherapy regimens may enhance the therapeutic efficacy of these drugs for EBV-driven lymphoproliferative disease in patients.
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PMID:Lytic induction therapy for Epstein-Barr virus-positive B-cell lymphomas. 1474 54

Increased reactive oxygen species (ROS) production has been reported as a distinctive feature of different pathologies including cancer. Therefore, we assessed whether increased ROS production in the cancer microenvironment could be selectively exploited to develop a selective anticancer therapy. For this purpose, we constructed a novel chimeric promoter, based on a ROS-response motif located in the VEGF gene promoter placed, in turn, downstream of a second ROS-response motif obtained from the early growth response 1 (Egr-1) gene promoter. The activity of the chimeric promoter was largely dependent on variations in intracellular ROS levels and showed a high inducible response to exogenous H(2)O(2). Transient expression of the thymidine kinase (TK) gene driven by the chimeric promoter, followed by gancyclovir (GCV) administration, inhibited human colorectal cancer and melanoma cell growth in vitro and in vivo. Moreover, electrotransfer of the TK gene followed by GCV administration exerted a potent therapeutic effect on established tumors. This response was improved when combined with chemotherapeutic drugs. Thus, we show for the first time that a distinctive pro-oxidant state can be used to develop new selective gene therapeutics for cancer.
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PMID:Suppression of cancer growth by nonviral gene therapy based on a novel reactive oxygen species-responsive promoter. 1943 70