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:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In ventricular muscle, 3,5,3'-triiodo-L-thyronine (T3) stimulates the expression of the alpha-myosin heavy-chain (alpha-MHC) gene. To test for gene elements required for induction, a fragment of the alpha-MHC gene containing 2.9 kilobases of 5' flanking sequences and 420 base pairs of DNA 3' to the transcription initiation site was linked to the coding sequences of the bacterial chloramphenicol acetyltransferase (CAT) gene. The alpha-MHC fusion gene was introduced into primary cultures of fetal rat heart myocytes. Induction of the transfected gene was monitored by assaying CAT activity while endogenous alpha-MHC mRNA expression was measured by using a synthetic oligonucleotide probe complementary to sequences in the 3' untranslated region of the mRNA. Without T3, CAT activity was only slightly greater than background. When T3 at a final concentration of 10 nM was added to the cultures, CAT activity was increased 8-fold by 48 hr. The response time and doses of T3 required for induction of CAT activity and alpha-MHC mRNA in transfected cells were similar, suggesting that the synthetic and endogenous genes may have a common mechanism of control. When simian virus 40 enhancer and early promoter sequences were included in the construct, CAT activity was constitutively expressed, but it could be increased 7-fold by the addition of T3. Several deletions were introduced into the 5' flanking sequences of the alpha-MHC fragment and the effects on induction of CAT activity were examined. Progressive deletions of 5' sequences from positions -947 to -374 reduced but did not eliminate induction of CAT activity, suggesting that more than one region may be required for optimal induction by thyroid hormone. The results indicate that DNA sequences required for efficient induction by T3 are present in the 5' flanking sequences of the alpha-MHC gene.
...
PMID:Thyroid hormone regulates expression of a transfected alpha-myosin heavy-chain fusion gene in fetal heart cells. 347 99

Retinoic acid (RA) is widely involved in the control of cell proliferation and differentiation, as well as embryo pattern formation. Transcription of the oncodevelopmental protein, alpha-fetoprotein (AFP), is stimulated by retinoic acid (RA) in neoplastic cells. To study RA regulation of AFP gene expression, the 5'-flanking region of AFP gene was cloned and analyzed. In the present study, transfection of deletion mutants and sequence analysis revealed a retinoid X receptor response element (AFP-RXRE) located at position -139 to -127 of the AFP promoter. Synthetic AFP-RXRE was ligated into a reporter construct with the heterologous promoter and chloramphenicol acetyltransferase (CAT). AFP-RXRE conferred a marked RA responsiveness in the cotransfection with retinoid X receptor (RXR), but not with retinoic acid receptors (RARs). Consistent with these data, only RXR bound to AFP-RXRE with high affinity in the mobility shift assays. Chicken ovalbumin upstream promoter transcription factor (COUP-TF), an orphan member of the steroid/thyroid hormone superfamily, also demonstrated specific binding activity to AFP-RXRE in vitro. In cotransfection assays, COUP-TF dramatically repressed the transactivation of RXR on AFP-RXRE. The mechanism of repression by COUP-TF may involve the mutual occupancy of the AFP-RXRE binding site between RXR and COUP-TF.
...
PMID:Transactivation and repression of the alpha-fetoprotein gene promoter by retinoid X receptor and chicken ovalbumin upstream promoter transcription factor. 751 61

Estrogen therapy has been reported to cause multiple alterations in hemostasis and to increase blood levels of several procoagulants, including Hageman factor [factor XII (FXII)]. Liver FXII gene expression has been investigated in ovariectomized rats, treated or not with 17 beta-estradiol. A 6-fold stimulation of FXII gene transcription was observed in treated compared to untreated animals, indicating that 17 beta-estradiol is able to induce FXII gene expression in vivo. We have recently shown that human FXII promoter contains an imperfect palindrome, 5'-GGGCAnnnTGACC-3', at position -43/-31 resembling the consensus estrogen-responsive element (ERE). Portions of different length of the FXII promoter were fused to the chloramphenicol acetyltransferase (CAT) coding sequence and transiently cotransfected with human estrogen receptor (ER) into NIH3T3 and HepG2 cells in the presence or absence of 17 beta-estradiol. A 230-base pair fragment of FXII promoter, spanning nucleotides - 181/49, conferred a strong estrogen responsiveness to the CAT reporter gene, suggesting that a functional ERE resides in this region. Cognate receptors, such as those for thyroid hormone or retinoic acid, did not stimulate CAT activity. Gel mobility assays demonstrated a specific interaction between ER and the 230-bp FXII promoter fragment containing the putative ERE palindrome. Similar results were obtained when an oligonucleotide spanning the consensus ERE was used; the complex between ER and FXII promoter sequences was supershifted after the addition of an anti-ER monoclonal antibody. Insertion of FXII-ERE into the heterologous thymidine kinase promoter conferred a strong estrogen responsiveness that was abolished by mutations of the 5'-half of the palindrome. These results represent the first demonstration at the molecular level of the regulation of a blood coagulation factor gene by 17 beta-estradiol as well as the first identification of a functional ERE within this class of genes.
...
PMID:Molecular basis of estrogen regulation of Hageman factor XII gene expression. 758 44

3,5,3,'-Triiodothyroacetic acid (Triac) has been used in therapy of resistance to thyroid hormone on an empirical basis and appears beneficial in some studies. We observed that the T3 analogs, Triac and 3,5,3'-triiodothyropropionic acid (Triprop), have a higher affinity for the thyroid hormone receptor-beta 1 (TR beta 1) than does T3 (2.7- and 1.8-fold, respectively), whereas the affinities of the three compounds for TR alpha 1 are the same. To evaluate whether T3 analogs would have a differential effect on TR beta 1 and TR beta 1 mutants and thus be a specific treatment for patients with resistance to thyroid hormone, we examined the induction of the transcriptional activation of wild-type (wt) TR alpha 1, TR beta 1, and mutant TR beta 1s by T3, Triac, and Triprop. The dose response of transcriptional activation by T3 analogs was measured by transient cotransfections with TRs and a rat malic enzyme-TRE fused to thymidine kinase (TK)-chloramphenicol acetyltransferase (CAT) in COS-1 cells. For TR alpha 1 wt, induction of CAT activity by T3 and Triac occurred at the same concentration. For TR beta 1 wt, Triac and Triprop showed a higher maximal activity than T3 (Tripro > Triac > T3) and reached 50% induction at a lower concentration than T3 (Tripro < Triac < T3). Induction of CAT activity in five mutant TR beta 1s (kindreds Mh, Mc, CL, Mf, and GH) was also analyzed. Even high levels of T3 analogs could not restore CAT activity to that of TR beta 1wt for any mutant. A dominant negative effect was produced by Mh, Mc, and Mf. Mutants CL and GH had a mild dominant negative effect depending on T3 analog concentrations and TREs. Cotransfection studies were performed using a rat malic enzyme-TK-CAT reporter plasmid to analyze the effects of hormones at near-physiological concentrations of T3 and Triac. Triac had a significantly higher transcriptional activation than T3 in Mc, CL, and GH, suggesting that Triac would have a beneficial effect to different degrees for different mutant TR beta 1s. Using mutants Mc and GH, further studies were carried out using rat GH and double palindromic and inverted palindromic TREs in COS-1 cells. On each TRE, 10 nmol/L Triac induced higher transcriptional activation in TR beta 1wt, mutant TR beta 1s, and TR beta 1wt plus mutant TR beta 1s (1:1 ratio) than the same dose of T3.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Triiodothyroacetic acid has unique potential for therapy of resistance to thyroid hormone. 760 51

Transcription of the gene for phosphoenolpyruvate carboxy-kinase (PEPCK) is stimulated by thyroid hormone (T3), glucagon (via cyclic AMP) and glucocorticoids. A region of the PEPCK promoter between -332 and -308 mediates the induction of transcription by T3. To characterize this region further, mutations were introduced into this region of the PEPCK promoter and the modified promoters ligated to the chloramphenicol acetyltransferase (CAT) reporter gene. Using these PEPCK-CAT vectors in transient transfections in HepG2 cells, it was found that T3 stimulates PEPCK transcription through two direct repeats of the AGGTCA motif located between nucleotides -330 and -319 [PEPCK-thyroid-hormone-responsive element (TRE)]. The beta form of the T3 receptor (TR beta) bound PEPCK-TRE as a homodimer but bound far more efficiently as a heterodimeric complex with the retinoid X receptor (RXR). An additional region called P3(I) (-250 to -234) is required for T3 responsiveness and binds members of the CCAAT-enhancer-binding protein (C/EBP) family. P3(I) contains an AGGTCA-like motif that can bind the TR beta-RXR heterodimer. Mutagenesis of this motif abolished TR beta-RXR binding without reducing T3 induction. Mutation of the C/EBP-binding site or insertion of a cyclic AMP-responsive-binding-protein site at P3(I) eliminated the T3 response. Our results indicate that T3 stimulation of PEPCK transcription is mediated by TR beta bound to PEPCK-TRE and requires C/EBP to be bound at the P3(I) site.
...
PMID:Regulation of phosphoenolpyruvate carboxykinase gene transcription by thyroid hormone involves two distinct binding sites in the promoter. 763 10

We have examined mechanisms of regulation of the human glycoprotein hormone alpha subunit gene by thyroid hormone (T3) and estradiol. Pituitary-derived GH3 cells were transiently transfected with chimeric constructs comprising between 1,500 and 98 base pairs of human alpha subunit gene 5'-flanking sequence fused to the bacterial gene encoding chloramphenicol acetyltransferase (h alpha CAT) and treated with T3 and estradiol, alone and in combination. In pituitary cells, 98 base pairs of alpha gene 5'-flanking sequence were sufficient to mediate both inhibition of alpha gene promoter activity by T3 and stimulation by estradiol; inhibition of the alpha promoter by T3 was antagonized by estradiol. Mutation of nucleotides essential for T3 receptor binding to the alpha gene thyroid hormone response element abolished the response of h alpha CAT expression to estradiol as well as T3. In contrast to pituitary GH3 cells, estradiol treatment alone had no effect on expression of either h alpha CAT or the endogenous alpha gene in JEG-3 choriocarcinoma cells cotransfected with a human thyroid hormone receptor expression vector, but estradiol antagonized suppression of both endogenous and transfected alpha promoter activity by T3. Gel mobility shift assays demonstrated specific binding of in vitro synthesized human estrogen receptor (ER) to the alpha gene thyroid hormone response element. These findings suggest that estradiol modulates expression of the human alpha subunit gene in pituitary and choriocarcinoma cells by direct binding of ER to the alpha gene promoter, and that interaction of ER with the alpha gene negative TRE accounts for the antagonistic effects of estradiol and T3.
...
PMID:Estradiol modulates thyroid hormone regulation of the human glycoprotein hormone alpha subunit gene. 769 20

In this study, we have demonstrated that retinoic acid (RA) and thyroid hormone (T3) stimulate the synthesis and release of human placental lactogen (hPL), one of the major secretory products of syncytiotrophoblast cells. Enzymatically, dispersed trophoblast cells from term placentas exposed continuously to RA (0.5 microM) and T3 (0.1 microM) for 5 days released significantly more hPL than control cells after 3 days of exposure (P < 0.001 in each instance). On days 4 and 5, the amounts of hPL released by cells exposed to RA and T3 were approximately 3- and 5-fold higher than those in control cells, respectively. The stimulation by both RA and T3 was dose dependent and was accompanied by stimulation of hPL messenger RNA levels. RA and T3 caused 3.5- and 5.6-fold increases, respectively, in chloramphenicol acetyltransferase activity in BeWo choriocarcinoma cells transfected transiently with a 2.3-kilobase (kb) fragment of the hPL promoter (-2300 to 2 basepairs) coupled to a chloramphenicol acetyltransferase reporter gene. Deletion construct analysis of the hPL promoter (2.3, 1.2, and 0.5 kb) indicated that the T3- and RA-responsive elements are localized -0.5 to -1.2 kb up-stream from the transcriptional start site (+1), where several consensus RA- and T3-responsive element sites are present. These results indicate that RA and T3 stimulate the synthesis and release of hPL by a mechanism involving hPL gene transcription and further support a role for these steroids in placental function.
...
PMID:Retinoic acid and thyroid hormone regulate placental lactogen expression in human trophoblast cells. 786 2

We have previously shown that retinoic acid (RA) induces differentiation in an osteoblastic cell line derived from embryonic rat calvaria and that RA has selective effects on zif268 gene expression in these preosteoblastic cells,distinct from those in more mature osteoblasts. In this study we demonstrate that the RA-dependent transcriptional increase in zif268 gene expression is mediated by the interaction of RA receptors (RARs) with a 17 base pair sequence in the zif268 promoter containing a single half-site motif (GTTCA), identical to each of the direct repeats seen in the RAR beta 2 gene. The sequence appears relatively RA-specific, since the zif268 RA-responsive element is not activated by 1,25-dihydroxyvitamin D3 or thyroid hormone (T3). However, cotransfection of RAR expression vectors and an SV-40 promoter chloramphenicol acetyltransferase (CAT) construct containing the single zif268 RA-responsive motif into CV-1 cells demonstrates that the alpha-, beta-, and gamma-RARs transactivate through this element. Extensive mutagenesis of the zif268 promoter region containing the RA response element (RARE) motif confirms that the transactivation and nuclear protein binding activity of this region requires only the half-site motif. The direct involvement of RAR in this DNA-protein interaction has been demonstrated by competitive gel retardation analysis using consensus RAREs and super-shifting of the DNA-protein complex with mouse alpha- or gamma-RAR monoclonal antibodies. In addition, we found that cell-specific suppression of RA-stimulated zif268 gene expression can be attributed to a 29 base pair nucleotide sequence, located downstream of the RA-responsive region in the zif268 gene. This sequence appears to be bound specifically by nuclear protein(s) from several cell types, including osteoblasts. The presence of this sequence in cis to the zif268 RARE or the consensus beta RARE completely blocks the RA-responsiveness of the zif268 gene in differentiated osteoblasts. These data extend the broad spectrum of RA-responsive sequences necessary for DNA binding and transactivation to include regulation via single RARE half-site motifs and suggest that the lack of RA responsiveness in differentiated osteoblasts may be mediated by cell-specific suppression of gene expression.
...
PMID:Characterization of retinoic acid- and cell-dependent sequences which regulate zif268 gene expression in osteoblastic cells. 787 19

The beta-myosin heavy chain (beta-MyHC) gene is expressed in cardiac and slow skeletal muscles. To examine the regulatory sequences that are required for the gene's expression in the two compartments in vivo, we analyzed the expression pattern of a transgene consisting of the beta-MyHC gene 5' upstream region linked to the chloramphenicol acetyltransferase reporter gene. By using 5600 bp of 5' upstream region, the transgene was expressed at high levels in the slow skeletal muscles. Decreased levels of thyroid hormone led to the up-regulation of the transgene in both cardiac and skeletal muscles, mimicking the behavior of the endogenous beta-MyHC gene. After deleting the distal 5000 bp, the level of reporter gene expression was strongly reduced. However, decreased levels of thyroid hormone led to an 80-fold skeletal muscle-specific increase in transgene expression, even upon the ablation of a conserved cis-regulatory element termed MCAT, which under normal (euthyroid) conditions abolishes muscle-specific expression. In contrast, cardiac-specific induction was not detected with the deletion construct. These observations indicate that the cardiac and skeletal muscle regulatory elements can be functionally segregated on the beta-MyHC gene promoter.
...
PMID:Segregation of cardiac and skeletal muscle-specific regulatory elements of the beta-myosin heavy chain gene. 787 16

The cDNA for a member of the nuclear receptor family was cloned and named ubiquitous receptor (UR), since UR protein and mRNA are detected in many cell types. Rat UR/human retinoid X receptor alpha (hRXR alpha) heterodimers bound preferentially to double-stranded oligonucleotide direct repeats having the consensus half-site sequence AGGTCA and 4-nt spacing (DR-4). Coexpression of UR in COS-1 cells inhibited the stimulation of chloramphenicol acetyltransferase (CAT) reporter gene expression by hRXR alpha and human retinoic acid receptor alpha in the presence of all-trans-retinoic acid when DR-4 (but not DR-5) was present upstream of the promoter of a CAT reporter gene (DR-4-CAT). UR expression also inhibited the activation of a DR-4-CAT reporter gene by hRXR alpha and 9-cis-retinoic acid or by thyroid hormone receptor beta in the presence of thyroid hormone. However, in the absence of 9-cis-retinoic acid, UR in combination with hRXR alpha stimulation DR-4-CAT expression. Coexpression of thyroid hormone receptor markedly reduced this stimulation in the absence of thyroid hormone. UR may play an important role in normal growth and differentiation by modulating gene activation in retinoic acid and thyroid hormone signaling pathways.
...
PMID:Ubiquitous receptor: a receptor that modulates gene activation by retinoic acid and thyroid hormone receptors. 797 66


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

---