Disease relevance of tk

• A transient expression assay was used to measure the relative template activities of mutated tk genes in mouse L cells induced in trans by herpes simplex virus (HSV) [1].
• The gene, when introduced into five of the seven lines, carried a copy of the Escherichia coli supF gene attached beyond the 3' end of the HSV tk gene, but this did not affect the overall expression pattern [2].
• By injecting the transduced U937 cells in severe combined immunodeficient disease (SCID) mice, we generated a tumor which, during in vivo treatment with aza-C, maintained the high expression of lacZ and tk genes at the baseline values [3].
• In tk-deficient cell lines other then L-cells, such as mouse mastocytoma or rat hepatoma cells, a strong selection against the persistence of the expression construct was noted [4].
• The mouse lymphoma (L5178Y tk+/- 3.7.2C) in vitro mutagenesis assay can measure the genotoxic effects of a wide variety of chemical agents by inactivation of a single functional thymidine kinase (tk-1) gene [5].

High impact information on tk

• In vitro deletion of MMTV LTR sequences comprising the RNA initiation sequence and the "TATA" box do not effect hormonal regulation at the tk-specific mRNA start site [6].
• Assays capable of distinguishing between foreign and native TK indicated that at least one of the fetuses with the HSV tk gene had some TK enzyme of the HSV type and, therefore, at least one gene copy that was being accurately transcribed and translated to produce a functional protein, despite the absence of selective pressure [7].
• This suggests that the distance between the tk and galk genes in the Chinese hamster genome may be smaller than was previously thought [8].
• Similar to WHS patients, these animals were growth-retarded, were susceptible to seizures and showed midline (palate closure, tail kinks), craniofacial and ocular anomalies (colobomas, corneal opacities) [9].
• When females of one of the sexually dimorphic lines were treated with testosterone, the levels of HSV tk RNA and thymidine kinase activity were increased, although not to male levels [2].

Chemical compound and disease context of tk

• Adenoviral-mediated gene therapy delivery, combining the herpes simplex virus thymidine kinase gene (Ad-tk) with gancyclovir, has been evaluated as a treatment modality for numerous tumors in the laboratory and in the clinics [10].
• A retroviral vector for the enhanced expression of the herpes simplex virus thymidine kinase (HSV tk) gene was developed by using a tetracycline-responsive expression system (TRES) [11].
• Spontaneous and methyl methanesulfonate-induced trifluorothymidine-resistant mutants in mouse lymphoma L5178Y cells were analyzed using fluorescence in situ hybridization with mouse probes specific for chromosome 11, on which the tk gene is located, and chromosome 3, as the control [12].
• The tk gene was expressed with the regulated character after MCF/TRE/tk/Tet-On cells were implanted into the female SCID mice 7 days after Dox induction followed by intraperitoneally administration of GCV for 23 days [13].

Biological context of tk

• The genetic map around the tail kinks (tk) locus on mouse chromosome 9 [14].
• The mouse-lymphoma mutagenesis assay detects forward mutations at the heterozygous thymidine kinase (tk-1) locus in L5178Y tk+/- 3.7.2C cells [15].
• We show that one of the microsatellite markers mapped, D9Mit9, does not recombine at all with tk in our backcross [14].
• These consist of deletions of the functional allele, characterized by absence of a 6.3-kb tk-hybridizing band, and apparent point mutations, indistinguishable from wild-type on blots [15].
• The most gene-proximal promoter domain is located between 16 and 32 base pairs (bp) upstream of the tk mRNA cap site and contains a TATA homology [1].

Anatomical context of tk

• The concordant behavior of tk promoter mutants in microinjected frog oocytes and trans-induced mouse fibroblasts leads us to propose that recognition and activation of the HSV tk promoter is mediated by cellular transcription factors that are common to frogs and mice [1].
• We engineered the U937 human cell line with a retroviral vector consisting of the thymidine kinase suicide gene (tk), which induces sensitivity to ganciclovir (gcv) and through an IRES sequence, the bacterial beta-galactosidase gene (lacZ) as a marker gene [3].
• The vector contains a truncated tk gene for amplification under selective conditions, a sequence putatively supporting the replication of plasmid DNA in eukaryotic cells (murine autonomously replicating sequence) and an expression cassette for the cDNA to be studied [4].
• The retroviral vector (G1tTA-[tetOTkINa]R), in which tetO was used in the opposite orientation relative to viral transcription, was capable of transducing tk and neo genes into murine NIH 3T3 cells to yield a high level of tk gene expression [11].
• Analysis of CEA promoter-dependent tk gene expression showed significant activity of this promoter in several human and rat tumor-derived cell lines but not in rat primary hepatocytes and in mouse liver, whereas the CMV promoter was highly active in all cell types and tissues investigated [16].

Associations of tk with chemical compounds

• In contrast, cotransfection of the tk gene with polymers which do not assume Z-conformation such as, poly(dG) X poly(dC) or poly(dA-dT) X poly(dA-dT) showed no effect on the number of colonies formed [17].
• We found that potential Z-DNA forming polymers such as, poly(dG-m5dC) X poly(dG-m5dC) and poly(dG-dC) X poly(dG-dC), cotransfected with the tk gene decreased the level of Tk+ transformed colonies [17].
• We observe a high level of fl and tk reporter gene expression predominantly in the lungs after a single injection of the extruded DOTAP:cholesterol DNA liposome complexes by way of the tail vein, seen to be time- and dose-dependent [18].
• However, one such tk-containing clone (C6) spontaneously lost its ability to respond to interferon by inducing an antiviral state although it retained its ability to induce the enzyme oligo(2'-5' A)-synthetase [19].
• Using a CMV promoter driven hygromycin/thymidine kinase (hyg/tk) fusion gene as both our dominant and negative selectable marker, we targeted the Cftr locus very efficiently but only identified false runs after the negative selection step [20].

Other interactions of tk

• This panel allowed us to map five microsatellite loci as well as d and Mod-1 with respect to tk [14].
• The subcutaneous tumors were surgically resected and the tumor bed was bathed with saline or Ad-tk [10].
• Decreasing expression of Dkk1 results in hemivertebral fusions in progressively more anterior positions, with severity increasing from tail kinks to spinal curvature [21].

Analytical, diagnostic and therapeutic context of tk

• Sequence analysis of tka(-)-1 and tkb(+)-1 alleles in L5178Y tk+/- mouse-lymphoma cells and spontaneous tk-/- mutants [15].
• In 65% (pnp vector), 75% (ntr vector) and 37% (tk vector) of these mice the tumors stopped growing or vanished and the animals remained tumor free for the 25 weeks of the experiment, whereas all mice of the control groups had to be killed because of the tumor growth [22].
• In this study, two tumor models were used to evaluate the effects of Ad-tk gene therapy as an adjuvant to surgery [10].
• We demonstrate cationic lipid-mediated noninvasive monitoring of reporter gene expression of firefly (Photinus pyralis) luciferase (fl) and a mutant herpes simplex virus type I thymidine kinase (HSV1-sr39tk, tk) in living mice using a cooled charge coupled device (CCD) camera and positron emission tomography (PET), respectively [18].
• The tk gene was detected in the transformants by in situ hybridization analysis [23].

References