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)

Previous analysis of the human interferon-gamma (IFN-gamma promoter indicated that the region of DNA from -251 to -215 (designated here as BE (binding element)) possessed silencer activity, as deletion of this region caused an increase in promoter activity. Based on this finding, we have conducted a series of experiments to characterize BE function and analyze the binding proteins which interact with this region. Transient transfection assays in the Jurkat T cell line revealed that the BE region possesses silencer activity, which is orientation-dependent when reinserted 5' to the IFN-gamma core promoter. However, when the BE region was inserted in front of a heterologous promoter (thymidine kinase (TK)), a mild enhancer activity was observed. Utilizing the electrophoretic mobility shift assay, we have identified two major DNA-protein complexes (designated as S and E complexes) which interact with this region. Mutational analysis indicated that the silencer activity observed with the IFN-gamma promoter correlated with the S complex and the enhancer activity correlated with the E complex. Preliminary characterization of these two DNA-protein complexes has demonstrated the presence of multiple proteins in each complex. We have found that the S protein complex has a recognition sequence similar to the nuclear factor AP2, and we have identified the nuclear factor Yin-Yang 1 (YY1) as one of the proteins in the E complex.
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PMID:Characterization of a silencer regulatory element in the human interferon-gamma promoter. 792 77

Site-specific mutagenesis of the highly conserved milk box (-140 to -110) region suggested that beta-casein expression is regulated by a hormone-mediated relief of repression (M. Schmitt-Ney, W. Doppler, R. K. Ball, and B. Groner, Mol. Cell. Biol. 11:3745-3755, 1991). However, when this sequence was placed upstream of a heterologous thymidine kinase promoter, it activated reporter gene expression. This apparent paradox was resolved when the trans-acting factor YY1, capable of acting as both a positive and negative regulator, was shown to interact with the milk box region, using bacterially expressed YY1 and specific oligonucleotide and antibody competition experiments. Second, it was demonstrated that extracts prepared from several cell types contained a protein(s) interacting with the mammary gland-specific factor (MGF) binding site, previously shown to be required for beta-casein promoter activity (Schmitt-Ney et al., Mol. Cell. Biol. 11:3745-3755, 1991). Sequence analysis of this site revealed similarity to the gamma interferon-activated sequence, suggesting that MGF may be related to the stat91 signaling protein. Finally, using an oligonucleotide encompassing both the YY1 and MGF sites, we detected a slow-mobility complex only in extracts from mammary glands at late pregnancy and lactation (lactation-associated complex [LAC]). Site-specific mutation of the YY1 binding site led to an enhancement in LAC DNA binding activity, while mutation of the MGF site decreased detectable LAC. These results support a model in which lactogenic stimuli lead to a decrease in YY1 binding, and subsequent increased formation of LAC at a nearby binding site, to stimulate beta-casein transcription.
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PMID:YY1 represses beta-casein gene expression by preventing the formation of a lactation-associated complex. 811 9

Human papillomavirus type 16 (HPV16) induces squamous intraepithelial lesions of the cervical mucosa which may develop into invasive cancer. The expression of viral oncogenes in advanced neoplasias appears increased relative to the proliferating cell layers of low grade lesions raising questions about molecular mechanisms of deregulation of transcription. In a lymph node metastasis of a cervical cancer, we observed full-length HPV16 plasmids and molecules with a small deletion, which was mapped to the long control region (LCR). Both wild type and shortened LCR were amplified by PCR, cloned into the promoter test plasmid pBLCAT6 and sequenced to identify a 107 bp deletion from position 7794 to 7901 in the short LCR. CAT expression in cervical cancer-derived HT3, SiHa and CaSki cells appeared 5- to 6-fold increased under the control of the short LCR. This could be traced back to elevated levels of mRNA initiated at the viral oncogene promoter. A slight further increase in CAT expression was noted in the presence of the HPV16 E2 protein which is probably due to the deletion of one E2 binding site and consequent relief from E2 repression. Computer-assisted sequence analysis and band-shift experiments with purified YY1 protein and wild type or mutated oligonucleotides identified four binding sites for this cellular transcriptional repressor within the promoter-proximal segment of the HPV16 LCR, three of which were removed by the deletion. A LCR fragment comprising these YY1 binding sites was cloned in front of the heterologous thymidine kinase gene promoter and suppressed CAT expression 3- to 4-fold.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The E6/E7 promoter of extrachromosomal HPV16 DNA in cervical cancers escapes from cellular repression by mutation of target sequences for YY1. 813 27

Human involucrin whose gene transcription is directed by a 2456-nucleotide (nt) 5'-noncoding region is a structural component of the epithelial cornified layer. Transient transfection assays demonstrated that this region is transcriptionally active in multiplying keratinocytes and is enhanced by 2 mM CaCl2 treatment. Calcium-independent transcriptional activity and the interaction with the AP-1 transcriptional factor was located on the proximal part (nt -159 to -1) of the 5'-noncoding region. However, CaCl2 responsiveness was mapped to a distal 1185-nt fragment (nt -2456 to -1272). Moreover, this fragment potentiated the Herpes simplex thymidine kinase promoter in normal keratinocytes and is responsive to calcium treatment in a cell type-specific manner. Interestingly, the absence of a 491-nt fragment located between the two enhancer domains (nt -651 to -160) resulted in transcriptional activation in multiplying keratinocytes. This fragment interacts with AP-1 and the YY1 transcriptional silencer. It is concluded that human involucrin 5'-noncoding region contains at least three regulatory domains, a distal CaCl2-responsive enhancer, a putative transcriptional silencer (that interacts with AP-1 and YY1), and a proximal enhancer/promoter (that interacts with AP-1). Thus, this study demonstrates the presence of particular transcriptional factors can potentially regulate the human involucrin expression.
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PMID:Transcriptional analysis of the 5'-noncoding region of the human involucrin gene. 855 Jun 12

The 5' upstream region of bovine growth hormone (bGH) gene was analyzed. When the region between nucleotides -336 and -240 was deleted, the expression of the reporter chloramphenicol acetyltransferase (CAT) gene increased about 5 fold in HeLa cells and 2.2 fold in rat GH3 cells which produce growth hormone. This region was named negative regulatory site (NRS). When NRS was inserted in front of promoter for rat growth hormone (rGH) gene or human thymidine kinase (TK) gene, the CAT activity decreased by 75-80% in HeLa cells and 5-30% in GH3 cells. It also repressed the expression of CAT gene from several promoter-enhancer combinations tested. By fine deletion analysis negative elements in the NRS were mapped and found to contain sequences similar to the binding elements of YY1.
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PMID:Identification of a negative regulatory site in the upstream region of bovine growth hormone gene. 860 91

The mouse cytochrome oxidase (COX) Vb promoter contains three sequence motifs with partial or full consensus for YY-1 and GTG factor binding and a CArG box, located between positions -480 and -390. Individually, all three motifs stimulated transcription of the TKCAT promoter, and bound distinctly different proteins from the liver and differentiated C2C12 nuclear extracts. Collectively, these motifs, together with the downstream flanking sequence, -378 to -320, suppressed the transcription activity of heterologous promoters, thymidine kinase-chloramphenicol acetyltransferase (TKCAT) and COXIV/CAT. The transcription activities of both TKCAT and COXIV/CAT constructs were induced 3-4-fold during induced myogenesis of C2C12 cells. The downstream CArG-like motif binds transcription factor YY-1, while the upstream YY-1-like motif binds to a yet unidentified factor. Co-expression with intact YY-1, but not that lacking the DNA binding domain suppressed the transcriptional activity. Mutations targeted to the CArG-like motif abolished the suppressive effect of the negative enhancer and the inducibility of the promoter during myogenic differentiation. Our results suggest that the activity of the negative enhancer may determine the level of expression of the COX Vb gene in different tissues.
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PMID:Regulation of murine cytochrome oxidase Vb gene expression in different tissues and during myogenesis. Role of a YY-1 factor-binding negative enhancer. 903 8

Multiple regulatory elements and intricate protein-DNA interactions mediate the transcription of the human histone H4 genes in a cell growth-dependent manner. Upon analysis of the regulatory elements of the FO108 histone H4 gene, we identified several potential YY1 binding sites. In this study, we have analyzed the ability of the transcription factor YY1 to interact at these sites in vitro by using electrophoretic mobility shift assays in combination with oligonucleotide competition and antibody immunoreactivity. We show that YY1 specifically binds transcriptional regulatory elements at -340 nt (site III), -100 nt (site I) and at least two domains within the coding region of the histone H4 gene. To test if these elements were functionally responsive to YY1, we performed transient expression experiments in Drosophila S-2 cells transfected with heterologous reporter gene constructs driven by histone H4 gene segments fused to the thymidine kinase promoter. Co-expression of YY1 stimulated promoter activity of these constructs relative to the reporter construct lacking histone H4 gene fragments. Our results suggest that YY1 contributes to transcriptional regulation of the histone H4 gene through interactions at multiple regulatory elements.
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PMID:Multiple interactions of the transcription factor YY1 with human histone H4 gene regulatory elements. 1002 10

Deficiency of acid maltase (acid alpha-glucosidase), a lysosomal enzyme that degrades glycogen, results in glycogenosis type II, an autosomal recessive disease whose manifestations and severity largely depend on the level of residual enzyme activity. Previous studies have established that there are transcriptional control elements in the first intron; in particular a silencer responsive to Hes-1 and YY1 has been identified in the human hepatoma line, HepG2. This region functions as an enhancer in human fibroblasts. Here we have localized a silencer active in fibroblasts to a nearby 25-bp element in intron 1. This element repressed thymidine kinase promoter activity by about 50% in both orientations in human fibroblasts. This silencer, as with the previous one, is tissue specific since constructs containing this region are inactive in HepG2 cells. Electrophoretic mobility shift assay revealed three proteins specifically binding to the element in fibroblasts, and site-directed mutagenesis analysis indicated that all the three proteins binding to the element contribute to the silencer function. The data may be helpful for designing therapy to increase the level of enzyme, particularly when, as in most adults with the disease, there is reduced production of structurally normal enzyme.
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PMID:Identification and characterization of a tissue-specific silencer element in the first intron of the human acid maltase gene. 1151 24

Various studies point to the potential role of combinatorial action of transcription factors as a mechanism to achieve the complexity of eukaryotic gene control with a finite number of regulatory proteins. Our previous work has focused on interactions involving the E2F family of transcription factors as an example of combinatorial gene control, leading to the identification of TFE3 and YY1 as transcription partners for several E2F proteins. We now show that additional E2F target genes share a common promoter architecture and are also regulated by the combined action of TFE3 and E2F3. In contrast, the thymidine kinase (TK-1) promoter is also regulated by E2F3 but independent of TFE3. Other promoters exhibit distinct specificity in the interaction with E2F proteins that includes a role for E2F1 but not E2F3, examples where both E2F1 and E2F3 are seen to interact, and promoters that are regulated by TFE3 but independent of an E2F. We propose that these examples of combinatorial interactions involving E2F proteins provide a basis for the specificity of transcription control in the Rb/E2F pathway.
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PMID:Combinatorial gene control involving E2F and E Box family members. 1501 47