Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
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 regulatory protein ICP4 is required for induced expression of HSV early and late genes, yet the mechanism by which this occurs is not known. We examined the promoter and flanking sequences of the HSV early gene that encodes thymidine kinase for the ability to interact specifically with ICP4 in gel retardation assays. Protein-DNA complexes containing ICP4 were observed with several distinct regions flanking the tk promoter. cis-Acting elements that interact with cellular transcription factors were apparently not required for these interactions to form. Purified ICP4 formed protein-DNA complexes with fragments from these regions, and Southwestern (DNA-protein blot) analysis indicated that the interaction between ICP4 and these sequences can be direct. None of the tk sequences that interact with ICP4 contains a consensus binding site for ICP4 (S. W. Faber and K. W. Wilcox, Nucleic Acids Res. 14:6067-6083, 1986), reflecting the ability of ICP4 to interact with more than one DNA sequence. A mutated ICP4 protein expressed from the viral genome that retains the ability to bind to a consensus binding site but does not bind specifically to the identified sites flanking the tk promoter results in induced transcription of the tk gene. These data support hypotheses for ICP4-mediated transactivation of the tk promoter in Vero cells that do not require the intrinsic ability of ICP4 to bind specifically in or near the promoter of the tk gene.
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PMID:Functional relevance of specific interactions between herpes simplex virus type 1 ICP4 and sequences from the promoter-regulatory domain of the viral thymidine kinase gene. 215 35

Estrogenic endocrine-disrupting chemicals abnormally stimulate vitellogenin gene expression and production in the liver of many male aquatic vertebrates. However, very few studies demonstrate the effects of estrogenic pollutants on brain function. We have used polyethylenimine-mediated in vivo somatic gene transfer to introduce an estrogen response element-thymidine kinase-luciferase (ERE-TK-LUC) construct into the brain. To determine if waterborne estrogenic chemicals modulate gene transcription in the brain, we injected the estrogen-sensitive construct into the brains of Nieuwkoop-Faber stage 54 Xenopus laevis tadpoles. Both ethinylestradiol (EE2; p < 0.002) and bisphenol A (BPA; p < 0.03) increased luciferase activity by 1.9- and 1.5-fold, respectively. In contrast, low physiologic levels of 17ss-estradiol had no effect (p > 0.05). The mixed antagonist/agonist tamoxifen was estrogenic in vivo and increased (p < 0.003) luciferase activity in the tadpole brain by 2.3-fold. There have been no previous reports of somatic gene transfer to the fish brain; therefore, it was necessary to optimize injection and transfection conditions for the adult goldfish (Carassius auratus). Following third brain ventricle injection of cytomegalovirus (CMV)-green fluorescent protein or CMV-LUC gene constructs, we established that cells in the telencephalon and optic tectum are transfected. Optimal transfections were achieved with 1 microg DNA complexed with 18 nmol 22 kDa polyethylenimine 4 days after brain injections. Exposure to EE2 increased brain luciferase activity by 2-fold in males (p < 0.05) but not in females. Activation of an ERE-dependent luciferase reporter gene in both tadpole and fish indicates that waterborne estrogens can directly modulate transcription of estrogen-responsive genes in the brain. We provide a method adaptable to aquatic organisms to study the direct regulation of estrogen-responsive genes in vivo.
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PMID:Assessment of estrogenic endocrine-disrupting chemical actions in the brain using in vivo somatic gene transfer. 1574 23