Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Milk protein gene expression is regulated by the synergistic interactions of several lactogenic hormones, including insulin, PRL, and glucocorticoids. Whey acidic protein (WAP) gene expression is highly dependent on glucocorticoids, and to a lesser extent than casein gene expression, on the presence of PRL. Previous studies have demonstrated that a distal DNase I hypersensitive site in the rat WAP gene 5'-flanking region containing several binding sites for nuclear factor I is required for high level WAP gene expression in transgenic mice. In this study several specific glucocorticoid receptor (GR) binding sites were identified flanking these nuclear factor I sites using an in vitro DNase I footprinting assay with baculovirus-expressed GR. These sites were able to confer dexamethasone inducibility to a heterologous thymidine kinase-chloramphenicol acetyltransferase reporter gene construct in transient cotransfection experiments with GR in CV1 cells. Administration of dexamethasone to adrenal-ectomized mice carrying the +2020 rat WAP transgene during lactation demonstrated that glucocorticoids are required to maintain transgene expression in the mammary gland. Furthermore, glucocorticoid-induced changes in transgene expression were correlated with the appearance of DNase I hypersensitive sites. These results indicate that at least part of glucocorticoid regulation of WAP gene expression is mediated through the direct interaction of GR with glucocorticoid response elements in the distal promoter region resulting in steroid hormone-dependent alterations in chromatin structure.
...
PMID:Glucocorticoid regulation of rat whey acidic protein gene expression involves hormone-induced alterations of chromatin structure in the distal promoter region. 785 50

We have established a system in which we observe a synergistic interaction between insulin and glucocorticoids. This includes chimeric genes constructed to contain synthetic glucocorticoid-responsive elements, 5' of the HSV thymidine kinase promoter and the chloramphenicol acetyltransferase reporter gene. The magnitude of induction of gene expression by glucocorticoid was dependent on the number of GREs. Insulin alone had virtually no effect on the expression of any of these genes but together with dexamethasone acted in a synergistic manner. This synergy diminished as the number of GREs in the promoter increased. The synergy is independent of promoter sequences other than the GREs and a functional TATAA box. Three different approaches demonstrate that the effect of insulin is not directly on the glucocorticoid signal transduction pathway. Insulin does not change the dose-response relationship for dexamethasone. The effect of insulin is independent of the intracellular concentration of glucocorticoid receptor. The effect is independent of any specific domain of the glucocorticoid receptor. The target of insulin action is likely to be part of the normal host cell transcriptional initiation complex or a putative adaptor molecule.
...
PMID:Insulin enhances glucocorticoid receptor-mediated induction of gene expression independent of a specific insulin response element. 786 47

Transcription of the phosphoenolpyruvate carboxykinase gene is stimulated by glucocorticoids, retinoic acid, and cAMP and is dominantly inhibited by insulin and phorbol esters. The glucocorticoid response is mediated by a complex regulatory unit that consists of two glucocorticoid receptor (GR) binding sites (GR1 and GR2) and two adjacent accessory factor elements (AF1 and AF2). Deletion of either the AF1 or the AF2 element results in a 50-75% reduction of the glucocorticoid response. In addition to their accessory role in glucocorticoid action, the AF1 and AF2 elements mediate retinoic acid and insulin/phorbol ester effects, respectively. Site-directed mutagenesis was performed on AF1 and AF2 to precisely locate the sequences responsible for accessory activity in each element. The glucocorticoid accessory activity of the AF1 element maps to the same 12-base pair sequence (TGACCTTTGGCC) involved in the response of the PEPCK gene to retinoic acid. The glucocorticoid accessory activity of the AF2 region maps to the same 10-base pair sequence (TGGTGTTTTG) responsible for mediating the insulin and phorbol ester responses through this element. The AF1 and AF2 elements bind different sets of nuclear proteins, and this binding is not qualitatively or quantitatively affected by treatment of the rat H4IIE hepatoma cells with retinoic acid (AF1) or insulin (AF2). AF2 functions in a heterologous context (a consensus glucocorticoid response element and the thymidine kinase promoter), whereas AF1 functions in this context only if the retinoic acid receptor is overexpressed in the cells. These results show that the AF1 and AF2 elements affect the glucocorticoid response through different protein DNA interactions, and that a small sequence in each serves multiple functions. Together with GR1 and GR2, they form a complex hormone response unit which provides an integrated response of the phosphoenolpyruvate carboxykinase gene to a variety of positive and negative signals.
...
PMID:Integration of multiple signals through a complex hormone response unit in the phosphoenolpyruvate carboxykinase gene promoter. 805 68

Tyrosine aminotransferase gene expression is confined to parenchymal cells of the liver, is inducible by glucocorticoids and glucagon, and is repressed by insulin. Three enhancers control this tissue-specific and hormone-dependent activity, one of which, located at -11 kb, is implicated in establishing an active expression domain. We have studied in detail this important regulatory element and have identified a 221-bp fragment containing critical enhancer sequences which stimulated the heterologous thymidine kinase promoter more than 100-fold in hepatoma cells. Within this region, we have characterized two essential liver-specific enhancer domains, one of which was bound by proteins of the hepatocyte nuclear factor 3 (HNF3) family. Analyses with the dedifferentiated hepatoma cell line HTC suggested that HNF3 alpha and/or -gamma, but not HNF3 beta, are involved in activating the tyrosine aminotransferase gene via the -11-kb enhancer. Genomic footprinting and in vitro protein-DNA binding studies documented cell-type-specific binding of ubiquitous factors to the second essential enhancer domain, which by itself stimulated the thymidine kinase promoter preferentially in hepatoma cells. These results will allow further characterization of the role of these enhancer sequences in developmental activation of the tyrosine aminotransferase gene.
...
PMID:The distal enhancer implicated in the developmental regulation of the tyrosine aminotransferase gene is bound by liver-specific and ubiquitous factors. 810 32

This study investigates whether insulin (a differentiation factor for lens epithelial cells) acts as a survival factor. In the absence of insulin, 6-day embryonic chicken lens epithelial explants undergo apoptosis as shown by changes in cell morphology, DNA fragmentation, and loss of trypan blue exclusion. Insulin inhibits these changes and promotes survival of the cells. Aurintricarboxylic acid suppresses the apoptosis of lens explants. In contrast to 6-day embryonic explants, 19-day embryonic explants survive in the absence of insulin, presumably due to an endogenous survival factor. To explore the mechanism of the action of insulin as a survival factor for 6-day embryonic lens explants, we compared the pattern of cell cycle markers (c-fos, c-jun, c-myc, p53, histone H3, thymidine kinase, and cyclin B) in both apoptotic and differentiating lens explants. In the presence of insulin, the expression of c-fos and c-jun was down-regulated after an initial induction. Expression of these genes was also induced in the absence of insulin, but mRNA levels remained elevated as the cells underwent apoptosis. In contrast, expression of c-myc, p53, histone H3, thymidine kinase, and cyclin B showed only minor differences in differentiating and apoptotic cells. Since c-fos and c-jun have been shown to play a role in apoptosis in other cell types, the ability of insulin to regulate expression of these genes may be central to its ability to act as a survival factor for lens epithelial cells.
...
PMID:Insulin regulates expression of c-fos and c-jun and suppresses apoptosis of lens epithelial cells. 854 23

The amylin (IAPP) and insulin genes are coexpressed in the pancreatic beta-cell and share related promoter elements that may bind similar islet transcription factors. The observation that these promoter elements contain AT-rich subdomains suggests that homeobox proteins may be important for the regulation of both insulin and amylin gene transcription. We show here that the LIM domain homeobox protein isl-1 activates the rat amylin promoter in both fibroblast and islet cell lines. Mutation of the rAMY promoter TAAT motifs was associated with a marked reduction in both basal and isl-1 -dependent transcriptional activity. The isl-1 homeodomain binds to the AT-rich AMY element (-156 to -137) in the human amylin (hAMY) gene promoter, and electrophoretic mobility shift assay experiments using isl-1 specific antiserum detected the formation of an hAMY-isl-1 complex using nuclear extract from InR1 -G9 islet cells. Although isl-1 binds to both the insulin and amylin gene promoter elements in vitro, these sequences display marked differences in their relative transcriptional properties when ligated adjacent to a heterologous promoter and transfected into InR1 -G9 islet cells. The insulin gene E2 sequence that binds isl-1 (-230 to -208) functions as a negative element, whereas the hAMY sequence activates the thymidine kinase promoter in islet, but not nonislet, cell lines. Transfection of isl-1-depleted isl-1 (AS)InR1 -G9 cell lines demonstrated that the E2 element continued to repress thymidine kinase promoter activity, whereas the positive transcriptional activity mediated by the AMY element was considerably reduced in isl-1 (AS)-InR1-G9 cell lines. These dat2 demonstrate that highly similar elements in islet hormone gene promoters display differential functional properties and support a role for the isl-1 homeodomain protein in the regulation of amylin, but not insulin, gene transcription.
...
PMID:Activation of amylin gene transcription by LIM domain homeobox gene isl-1. 883 53

A mini-human insulin gene and four derivatives mutated at several regions potentially involved in the regulation of gene expression were used to generate transgenic mouse lines. The effect of these mutations on the efficiency of gene expression and cell specificity was studied using three approaches: (1) Northern blot analysis using total RNA from pancreas and other organs, (2) radioimmunoassay to detect the human C-peptide in urine samples, and (3) immunocytochemistry of pancreas sections to examine whether expression of the transgene was still specifically expressed in beta-cells. Mutation of the cis-acting elements located between -238 and -206 (GCII and CTII motifs) resulted in a strong decrease of gene expression in the pancreas of transgenic mice, but it did not lead to complete extinction of the transgene expression. This region alone (-255/-202), when linked to the minimal Herpes simplex virus thymidine kinase gene (tk) promoter, failed to activate chloramphenicol acetyltransferase (CAT) gene expression in transfected insulinoma cells, while it was activated by the equivalent region of the rat insulin I gene. On the contrary, mutation of the DNA motifs located between -109 and -75 (GCI and CTI) or between -323 and -297 (CTIII) did not significantly affect the level of the human insulin gene expression in transgenic mice. Replacement of the insulin promoter (-58/+l) by the tk promoter did not alter its level of expression in transgenic mice. In all instances, expression of the different transgenes remained localized in the islet beta-cells. Altogether, these results indicate that the GCII-CTII motif is an important regulatory element for efficient expression of the human insulin gene in vivo, although it alone does not allow gene expression as it would require the association of other elements.
...
PMID:Human insulin gene expression in transgenic mice: mutational analysis of the regulatory region. 885 74

The effect of insulin on cell proliferation in vivo has been studied in hepatectomised streptozotocin-diabetic rats. The extent of cell proliferation in sham and hepatectomized-control, diabetic and insulin treated rats were monitored by determining DNA content and [3H]thymidine incorporation into DNA. The kinetic parameters of thymidine kinase a regulatory enzyme for DNA synthesis was also studied in these groups. The rate of DNA synthesis in liver of streptozotocin-diabetic rats was significantly higher 24 hrs post-hepatectomy compared to control and insulin treated diabetic groups. Kinetic studies of thymidine kinase revealed that there was no change in the Michaelis-Menten constant (Km) whereas maximum velocity (Vmax) was elevated in the diabetic hepatectomized groups compared to control and insulin treated hepatectomized groups. Thus our study elucidates the role of insulin in thymidine kinase activity and DNA synthesis.
...
PMID:Effect of insulin on DNA synthesis and kinetic parameters of thymidine kinase during liver regeneration. 895 97

The insulin gene is specifically expressed in pancreatic islet beta cells. Various cis-acting DNA elements in the 5'-flanking region of the human insulin gene were examined for their contribution to the transcriptional activity using sensitive human growth hormone (hGH) reporter plasmids. The hGH constructs, having successively deleted human insulin promoter sequences, were transfected to a pancreatic islet beta-cell line MIN6. The deletion of two GGAAAT (GG) motifs, GG2 at -145 to -140 bp and GG1 at -134 to -129 bp, decreased the transcriptional activity to 6.5% of that of the promoter sequence from -156 to +1 bp. The selective mutations in both GG motifs also decreased the transcriptional activity to 5.5%. One-base mutations of GG2 and GG1 decreased the transcriptional activity to 82 and 11%, respectively. The two-base mutations between GG2 and GG1 affected the transcriptional activity more strongly than those just outside the GG motifs. A single set of GG motifs in the upstream of thymidine kinase promoter increased the transcriptional activity to 216% compared to that of thymidine kinase promoter alone in MIN6 cells. With an electrophoretic mobility shift assay (EMSA), a nuclear factor in MIN6 cells was shown to bind the DNA fragments containing two GG motifs. This factor did not bind to another GGAAAT-like sequence at -313 to -305 bp in the human insulin gene. These results suggested that the GG motifs contributed to the cell-specific transcription of the human insulin gene in association with the binding of the sequence-specific nuclear factor.
...
PMID:GGAAAT motifs play a major role in transcriptional activity of the human insulin gene in a pancreatic islet beta-cell line MIN6. 896 Aug 27

We have investigated a possible delivery system for the rat preproinsulin II gene (rI2) utilising a recombinant adeno-associated virus (rAAV) vector system, with the long-term goal of engineering stably infected insulin-producing cell lines. The rAAV vector was chosen because it is a safe and nonpathogenic method for gene transfer. The plasmid pBC12BI (ATCC) was purified and digested with restriction enzymes SepI and StuI to release a fragment containing the Rous sarcoma virus long terminal repeat (RSV-LTR) promoter-driven rat preproinsulin II gene (rI2). Subsequently, the RSV-rI2 gene fragment was cloned into the BamHI site of rAAV vector plasmid pWP-19 to produce the rI2 recombinant plasmid designated pLP-1. The pWP-19 also encodes the AAV inverted terminal repeats for integration and replication and the herpes virus thymidine kinase promoter-driven gene for neomycin resistance (neoR). The cell line 293 (ATCC) was then cotransfected with pLP-1 and helper plasmid pAAV/AD, which is required for viral replication. The rAAV genome, now containing rI2, was rescued using adenovirus and packaged into mature AAV virions termed vLP-1. Finally, human pancreatic adenocarcinoma cells (HPAC; ATCC) were exposed to vLP-1, selected for G418 resistance, and screened for insulin production. Successful rescue was confirmed by Southern blot analysis using the rI2 gene probe derived from the original plasmid. The final titer of 1.25 x 10(9) particles/ ml was determined by DNA slot blots using pLP-1 as the standard, HPAC cells were infected with vLP-1 (termed HPAC/rI2). Integration of the rI2 genome in G418-resistant clones was confirmed by Southern blot analysis and again after 6 months in culture by amplification of the rI2 gene by PCR. Insulin gene transcription was confirmed by RT-PCR. We have developed a rAAV-mediated gene transfer system for the rat preproinsulin II gene. Successful transduction and stable integration of rI2 into HPAC was achieved. Production of insulin by HPAC/rI2 was confirmed by RIA and RT-PCR, validating this system as an effective approach to experimental gene therapy.
...
PMID:Construction of recombinant adeno-associated virus vector containing the rat preproinsulin II gene. 920 69


<< Previous 1 2 3 4 5 6 7 Next >>

---