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 herpes simplex virus (HSV) type 1 immediate-early protein ICP4 represses transcription of its own gene and possibly that of other immediate-early genes. In the present study, we analyzed the role that an ICP4 binding site present in two HSV-1 promoters plays in the level and kinetics of expression during HSV-1 infection. Wild-type and mutant forms of the IE-3 (ICP4) promoter and the latency associated promoter (LAP) were fused to the thymidine kinase (tk) coding sequences and transferred to the genome of an ICP4-deficient virus. Promoter mutants were constructed to assess the effect of the ICP4 binding site in the presence and absence of defined binding sites for cellular and other viral factors in the promoters. The activities of the promoter constructs were inferred from the level of tk mRNA seen following viral infection in the absence of ICP4, in Vero cells and in the presence of ICP4 in ICP4 expressing E5 cells. Kinetics of expression and the dependence on DNA synthesis for expression were examined following infection of E5 cells. In the presence of the ICP4 binding site in LAP and in IE3 promoters lacking TAATGARAT motifs, expression was maximal late after infection and was greatly reduced when DNA synthesis was inhibited. When the ICP4 binding site was removed, both LAP and the IE3 construct retaining an Sp1 site were more abundantly expressed and exhibited kinetics of expression indistinguishable from that of the tk promoter. In vitro, ICP4 repressed LAP transcription mediated by the general transcription factors and upstream activating proteins. Deletion of the ICP4 binding site not only relieved repression, but in the presence of USF activity, ICP4 further induced LAP transcription. The results of these experiments suggest a role for the repressor activity of ICP4 in the temporal regulation of HSV-1 transcription.
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PMID:The role of ICP4 repressor activity in temporal expression of the IE-3 and latency-associated transcript promoters during HSV-1 infection. 803 Feb 21

The murine alpha B-crystallin/small heat shock protein gene is expressed at high levels in the lens and at lower levels in the heart, skeletal muscle, and numerous other tissues. Previously we have found a skeletal-muscle-preferred enhancer at positions -427 to -259 of the alpha B-crystallin gene containing at least four cis-acting regulatory elements (alpha BE-1, alpha BE-2, alpha BE-3, and MRF, which has an E box). Here we show that in transgenic mice, the alpha B-crystallin enhancer directs the chloramphenicol acetyltransferase reporter gene driven by the alpha B-crystallin promoter specifically to myocardiocytes of the heart. The alpha B-crystallin enhancer was active in conjugation with the herpes simplex virus thymidine kinase promoter/human growth hormone reporter gene in transfected rat myocardiocytes. DNase I footprinting and site-specific mutagenesis experiments showed that alpha BE-1, alpha BE-2, alpha BE-3, MRF, and a novel, heart-specific element called alpha BE-4 are required for alpha B-crystallin enhancer activity in transfected myocardiocytes. By contrast, alpha BE-4 is not utilized for enhancer activity in transfected lens or skeletal muscle cell lines. Alpha BE-4 contains an overlapping heat shock sequence and a reverse CArG box [5'-GG(A/T)6CC-3']. Electrophoretic mobility shift assays with an antibody to serum response factor and a CArG-box-competing sequence from the c-fos promoter indicated that a cardiac-specific protein with DNA-binding and antigenic similarities to serum response factor binds to alpha BE-4 via the reverse CArG box; electrophoretic mobility shift assays and antibody experiments with anti-USF antiserum and heart nuclear extract also raised the possibility that the MRF E box utilizes USF or an antigenically related protein. We conclude that the activity of the alpha B-crystallin enhancer in the heart utilizes a reverse CArG box and an E-box-dependent pathway.
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PMID:Regulation of the murine alpha B-crystallin/small heat shock protein gene in cardiac muscle. 852 75