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)

We have studied the 5'-flanking sequences required for the transcriptional regulation of human epsilon-globin gene expression. A series of deletion mutants of the human epsilon-globin gene 5'-flanking sequences were constructed and linked to the bacterial chloramphenicol acetyltransferase gene. Expression of these constructs was tested in HeLa cells and the human erythroleukemia K-562 cells. By measuring chloramphenicol acetyltransferase activities and mRNA levels we found that the sequence between -177 and -392 base pairs (bp) relative to the mRNA initiation site exerts a negative effect on epsilon-globin promoter activity. This effect is more pronounced in HeLa cells compared with K-562 cells. To further characterize the negative control region we cloned the DNA sequence between -177 and -392 bp either 5' or 3' of the epsilon-globin promoter and in either orientation. Our data indicate that this negative control region inhibits the epsilon-globin promoter activity in a position- and orientation-independent manner, thus suggesting that it is a silencer. In addition, the silencer also inhibits the expression from the Herpesvirus thymidine kinase promoter. Sequence comparison reveals that there are three short regions within the silencer that share extensive homology with those found in other negative control DNA elements. Our results therefore indicate that an upstream silencer element is present in the epsilon-globin gene and that it may play an important role in the control of epsilon-globin gene expression during development.
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PMID:Identification of a transcriptional silencer in the 5'-flanking region of the human epsilon-globin gene. 274 86

At least two of the immediate-early (IE) products of herpes simplex virus-1 (HSV-1) are responsible for the activation of transcription from viral early promoters. This process appears not to be promoter specific since several unrelated viral and cellular plasmid-borne promoters can also be activated in short-term transfection assays. This paper describes experiments that show that cellular promoters integrated into the host genome can also be activated during viral infection, and that this process is brought about by IE gene products. Biochemically transformed cell lines were isolated following transfection of plasmids containing the human epsilon-globin promoter linked to the herpes thymidine kinase coding region (as selectable marker), and an unselected rabbit beta-globin gene. Infection of some, but not all, such cell lines with HSV-1 resulted in a rapid and considerable stimulation of the integrated epsilon- and beta-globin promoters. Both promoters could also be activated (albeit less efficiently) during pseudorabies virus infection, and after introduction by transfection of plasmids containing HSV IE genes. The implications of these results for viral-host interactions and the mechanism of viral-induced promoter activation are discussed.
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PMID:Activation of cellular promoters during herpes virus infection of biochemically transformed cells. 299 78

The possible regulatory role of DNA sequences situated 5' to the beta-maj globin gene was investigated by two types of assay. First, a long term transformation assay was used to measure the efficiency of transformation of TK- mouse (LATK-) and hamster (BHKTK-) fibroblast cells with DNA molecules made by covalently linking mouse and human DNA fragments to the herpes simplex virus (HSV-1) thymidine kinase (tk) gene in the plasmid pTK1. When the promoter regions from the mouse beta-maj globin or the human epsilon-globin genes are substituted for the viral promoter in the tk gene transformation occurs with 10-20% of the efficiency of the original plasmid. A fragment (H1), containing sequences between 344 and 1413 bp upstream from the mouse beta-maj globin cap site, almost completely abolishes transformation when inserted next to hybrid tk genes containing the mouse beta-globin or human epsilon-globin promoter but has no effect on the intact tk gene. The effect can be demonstrated with the H1 fragment in either orientation relative to the tk gene. Secondly, in transient expression assays the H1 fragment strongly inhibits transcription when covalently linked to the tk gene under control of either globin promoter, but not when linked to the tk gene with its own promoter. The H1 fragment contains 53 bp of purine-pyrimidine alternation (ACAT)n as part of a larger region potentially capable of adopting a Z-DNA conformation.
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PMID:A negative regulatory sequence near the mouse beta-maj globin gene associated with a region of potential Z-DNA. 608 13

Thymidine kinase negative (TK-) Friend cells were transformed with recombinant molecules carrying human globin genes and the thymidine kinase gene of herpes simplex virus type 1 DNA. Transformation frequencies of 1 transformant/microgram donor DNA/1 x 10(6) cells were obtained by standard procedures and this was increased 20- to 30-fold by treating recipient cells with dimethyl sulfoxide or glycerol. Transformed cell lines expressed thymidine kinase activity of viral origin as determined by its insensitivity to 0.2 mM dTTP and electrophoretic mobility in polyacrylamide gels. The physical status of donor DNA in the transformed cells was examined in Hirt precipitates and supernatants by Southern blot hybridization and spot hybridization techniques. This analysis showed that most donor sequences were present in a circular or concatenate configuration, but also was suggestive of some donor sequences being integrated into high molecular weight DNA. Expression of human globin genes and particularly the epsilon-globin gene in the transformed Friend cells was studied by Northern blot hybridization analysis.
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PMID:Transfer of human globin genes to erythroleukemic mouse cells. 632 49