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)

When a red cell nuclear extract (RCE) from adult chickens was injected into Xenopus oocytes along with the chicken beta globin gene, transcript levels were dramatically reduced compared to injection of DNA alone. The inhibitory action of the RCE was not specific to the beta globin gene since the Herpes thymidine kinase and Xenopus 5S RNA gene transcript levels were similarly reduced. Transcriptional repression was observed even after passage of the RCE through oocyte cytoplasm to the nucleus. The inhibitory activity binds to DNA cellulose, which suggests that the inhibitor either binds to DNA or associates with DNA-binding proteins. Nuclease digestion of the chromatin assembled on injected beta globin DNA revealed that inhibition was not associated with local changes in chromatin structure. Extracts from 9-d chicken embryonic erythroid cells, in which the endogenous beta globin gene is actively expressed, did not inhibit transcription. The inhibitory activity is, therefore, restricted to transcriptionally quiescent, adult erythrocytes. Since the inhibitory effects were seen with both polymerase II and III directed genes, we speculate that the activity may be part of the extreme transcriptional repression which occurs in the terminally differentiated erythrocyte.
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PMID:A chicken red cell inhibitor of transcription associated with the terminally differentiated state. 205 Jul 44

Present experimental data show that the synthesis of ribosomal protein S1 and PI protein was stimulated greatly by polyamines at the early stage after addition of putrescine in polyamine-requiring mutants of E. coli. No macromolecular synthesis was stimulated at this stage. Polyamine stimulation of the synthesis of these proteins probably plays an important role for cell growth. In polyamine-deficient bovine lymphocytes, protein synthesis became perturbed before RNA and DNA synthesis. Among enzymes concerned with DNA replication, thymidine kinase activity was most strongly influenced by polyamines. The activity in polyamine-deficient cells was only 7% of the level in normal cells. Judging from the amount of thymidine kinase mRNA and its distribution in polysomes, it was concluded that polyamines mainly regulate the synthesis of thymidine kinase at the level of initiation of protein synthesis. A polyamine-free protein synthetic system, established from components of rabbit reticulocytes, consisted of globin mRNA, salt-washed ribosomes, partially purified initiation factors, and pH 5 enzymes. Spermidine added to this system not only lowered the optimal magnesium concentration required for globin synthesis, but it also stimulated the globin synthesis 8- to 10-fold. The optimal spermidine concentration was 0.4 to 0.6 mM, a concentration similar to that in intact rabbit reticulocytes. The ratio of alpha to beta globin chains synthesized in the presence of spermidine and Mg2+ was approximately 1.0, while the ratio in the presence of only Mg2+ was approximately 1.5. The results strongly suggest that polyamines play an important role in rabbit reticulocyte protein synthesis.
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PMID:Regulation of protein synthesis by polyamines. 307 28

A recombinant plasmid pTKH beta GHp-3 carrying genomic human DNA sequences coding for the beta globin gene covalently linked to the thymidine kinase gene of HSV-1 and the ampicillin resistance region of a bacterial plasmid has been constructed. Using Bal 31 exonuclease, deletion mutants have been obtained from a single HpaI site located 800 bp upstream the 5' end of the beta globin gene and towards the cap site. Recipient mouse erythroleukemic Friend TK- cells were transformed with these molecules. Analysis of donor DNA sequences in transformed cells by Southern blotting and filter hybridization has demonstrated the presence of full length multiple copies. RNA isolated from transformed non-induced Friend cells, carrying one or the other of the donor human beta globin deletion mutants, has been analysed by Northern blot and spot hybridization analyses. Evidence has been obtained which suggests that DNA sequences located upstream the CCAAT box (at -76 bp from the cap site) are required for optimal levels of human beta globin specific RNA in transformed cells.
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PMID:Expression of the human beta globin gene and 5'-deletion mutants in erythroleukemic mouse cells studied by DNA mediated gene transfer. 620 56

A mixture of two recombinant plasmids was microinjected into mouse thymidine kinase-negative fibroblasts (L cells). One plasmid contained the thymidine kinase gene of herpes simplex virus type I and the other contained the human beta globin gene. Seven fibroblast colonies arising from injected cells incubated in hypoxanthine/aminopterin/thymidine medium were analyzed. These microinjected cells were shown to: (i) produce functionally active herpes simplex type I thymidine kinase enzyme, (ii) replicate the human beta globin gene, and (iii) produce human beta globin mRNA sequences at low levels. Thus, the genetic defect (lack of thymidine kinase activity) was corrected by the microinjected thymidine kinase gene, and a coinjected human beta globin gene was replicated and weakly expressed.
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PMID:Replication and expression of thymidine kinase and human globin genes microinjected into mouse fibroblasts. 625 80

Transformation, or DNA-mediated gene transfer, permits the stable introduction of new genetic information into a cell and therefore provides an opportunity to examine the expression of exogenous DNA sequences in the transformed host. A series of deletion mutants to analyze the sequences required for accurate and quantitative in vivo transcription of the herpes simplex virus (HSV) thymidine kinase (tk) gene has been constructed. Control of the efficiency of transcription as well as rough specification of the sites of initiation reside within sequences 40-110 nucleotides from the tk structural gene. The sequences responsible for induction of tk mRNA overlap this transcriptional control region. Analysis of the conformation of the integrated tk gene in the chromosome reveals that these DNA sequences are exquisitely sensitive to nuclease attack. The major heat shock gene of Drosophila and the human beta globin gene have also been introduced into murine cells to identify sequences responsible for induction of these finely regulated genes.
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PMID:The structure and function of a eukaryotic promoter. 630 29

Our interest in the cis-acting elements that promote the up-regulation of the beta globin gene has led to a systematic deletion analysis of portions of the beta globin gene in the context of the HS2 and gamma globin gene using transgenic mice. In constructs that delete the 5' region to only 265 bp, high-level, erythroid-specific expression was observed. Further deletion to 122 bp, however, results in significantly reduced expression levels. A substitution of a minilocus control region for the single HS2 site was also produced, resulting in increased beta globin expression over that seen with the HS2 alone. These results are consistent with the presence of an enhancer-like element between -122 and -265. In addition, a construct in which the entire beta globin gene promoter was replaced by a thymidine kinase promoter was tested. Interestingly, no expression was detected in these transgenic mice. This may indicate the requirement for an erythroid-specific promoter to drive this gene. Finally, the 3' region of the beta globin gene was deleted in order to examine the effect of a previously defined 3' enhancer region. With deletion of this region, the expression of the human beta globin gene in transgenic mice is unchanged relative to the parental constructs.
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PMID:Analysis of developmental switching in transgenic mice with 5' and 3' deletions in the human beta globin gene. 875 64