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)

Biological effects of retinoic acid (RA) are mediated through its binding to three closely related nuclear receptors (RAR alpha, RAR beta, and RAR gamma) belonging to the steroid-thyroid nuclear receptor family. RARs are able to modulate the transcription of specific genes by binding to responsive elements located in the promoter-enhancer region of these genes. As demonstrated by in situ hybridization, the distribution of each RAR type in the developing embryo, as well as in the adult, is not uniform. In this context, synthetic retinoids that would behave as selective ligands would be invaluable for studying the respective roles of each RAR type in cultured cells, whole animals, and embryos. Moreover, from a pharmacological point of view, such selective compounds may possess a higher therapeutic index and a lower teratogenic risk, because they might affect specific tissues and spare some others. As an approach to this problem, we have set up two complementary assays, (i) an in vitro binding assay to determine the Kd values of retinoids for RAR alpha, RAR beta, and RAR gamma and (ii) a functional assay in cultured cells to evaluate the potential of retinoids to transactivate, through their binding to one type of RAR, a reporter gene. The binding assay uses nuclear extracts of COS-7 cells transfected with vectors expressing RAR alpha, RAR beta, or RAR gamma. The functional assay is a measure of chloramphenicol acetyltransferase (CAT) activity in HeLa cells co-transfected with the expression vectors used in the binding assay and the reporter gene TRE-tk-CAT. Selective agonists for RAR alpha (Am80 and Am580) and RAR beta-RAR gamma (CD495 and CD564) were identified. However, compounds with pure RAR beta or RAR gamma selectivity have not yet been identified.
...
PMID:Selective high affinity retinoic acid receptor alpha or beta-gamma ligands. 165 91

The overproduction of P-glycoprotein, an integral membrane protein thought to function as a drug efflux pump, is the hallmark of the multidrug resistance phenotype. In murine multidrug resistant J774.2 cell lines, distinct mdr genes, mdr1a and mdr1b, encode unique P-glycoprotein isoforms. To examine the transcriptional regulation of the mdr1b gene, its promoter was isolated and characterized. The transcription initiation site was mapped by primer extension, and the 5'-flanking region was sequenced. Several potential regulatory elements were identified in this region. A transient expression vector was constructed by fusion of 540 base pairs of 5'-flanking sequence and part of the first untranslated exon to the chloramphenicol acetyltransferase (CAT) gene. When transfected into monkey kidney COS-1, rat pituitary GH3 or T47D human breast cells, the mdr1b 5'-flanking sequences were capable of driving CAT expression. Transient transfection studies using deletion subclones of the mdr1b-CAT construct were done to locate potential cis-acting sequences. The studies indicate the presence of cis-acting elements in the 5'-flanking region of the mdr1b gene. The implications of these findings for expression and regulation of the mdr1b gene are discussed.
...
PMID:Structural and functional analysis of the mouse mdr1b gene promoter. 167 Dec 22

The human genome contains a variety of elements similar in structure to retroviruses and retrotransposons. We have shown that the long terminal repeat (LTR) sequences of a large family of human retrovirus-like elements, RTVL-H, are heterogeneous in their ability to regulate the expression of linked genes. Although all of five LTRs tested could promote expression of the chloramphenicol acetyltransferase (CAT) gene, their relative promoter activities as well as range of activities varied widely. Several of the LTRs tested also exhibited bidirectional promoter activity either alone or when activated by an SV40 early enhancer. One LTR, H6, displayed strong promoter activity in human (NTera2D1, 293, Hep2), monkey (COS-1), and mouse (3T3) cells. In fact, the activity of this LTR was similar to that of the SV40 early promoter/enhancer in 293, COS-1, and 3T3 cells. RNA mapping studies have localized the transcription start site to the expected location in the H6 LTR. RTVL-H LTRs were also shown to contain sequences which could increase transcription from the human beta-globin promoter and be influenced by SV40 enhancer sequences. As the human genome contains several hundred related RTVL-H sequences and a similar number of solitary LTRs, these findings raise the possibility that RTVL-H LTRs could have diverse effects on the expression of adjacent cellular genes.
...
PMID:Functional heterogeneity of a large family of human LTR-like promoters and enhancers. 169 Aug 75

Glucocorticoid receptors are ligand-dependent transcription factors that are subject to down-regulation by their cognate ligand; however, the mechanisms mediating this physiological response are not completely understood. Since analysis of the human glucocorticoid receptor (hGR) cDNA sequence revealed the presence of sequences with homology to both positive and negative glucocorticoid regulatory elements, we have examined the potential of hGR to bind to the hGR cDNA by Southwestern blot analysis. The data revealed that glucocorticoid receptors exhibited specific binding to their own cDNA. To determine whether this binding was of functional significance in the down-regulation of glucocorticoid receptors, we analyzed the effect of glucocorticoids on hGR protein levels from COS 1 cells transfected with an hGR cDNA expression vector. These transfected cells produced intact hGR that were capable of ligand-dependent regulation of a co-transfected glucocorticoid-responsive reporter gene. Glucocorticoid treatment of hGR-transfected cells resulted in down-regulation of hGR (assayed by both glucocorticoid binding capacity and hGR protein levels) within 24 h of steroid administration. To determine if the glucocorticoid-induced down-regulation of transfected hGR was compatible with effects at the levels of receptor gene expression and RNA stability, we examined hGR mRNA steady state levels. Reductions from 2- to 6-fold were observed in hGR mRNA levels following glucocorticoid treatment of transfected COS 1 cells. This down-regulation of transfected hGR mRNA could not be attributed to either the Rous sarcoma virus promoter, which drives hGR expression, or to other sequences present in the vector plasmid since transcription of a related plasmid containing a chloramphenicol acetyltransferase gene in place of the hGR cDNA was not regulated by glucocorticoids. Down-regulation of hGR mRNA by glucocorticoids in transfected cells occurred in a time- and dose-dependent manner that is consistent with a glucocorticoid receptor-mediated process. Glucocorticoid-induced down-regulation of hGR mRNa steady state levels was not observed in COS 1 cells transfected with cDNAs encoding mutant hGR (defective in either steroid or DNA binding), which indicates that functional steroid and DNA binding domains of the expressed hGR were required for down-regulation. Interestingly, treatment of transfected COS 1 cells with the glucocorticoid antagonist RU486 also resulted in down-regulation of transfected hGR mRNA. Deletion analysis revealed that the region of the hGR cDNA that was responsible in part for the observed down-regulation in response to glucocorticoid was contained within a 1-kilobase restriction fragment (from base pair +527 to +1526).(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Human glucocorticoid receptor cDNA contains sequences sufficient for receptor down-regulation. 169 20

Insulin-like growth factor binding protein-3 (IGFBP-3) can modulate the mitogenic and metabolic effects of the insulin-like growth factors (IGFs). IGFBP-3 protein levels are developmentally regulated and influenced by a number of hormonal stimuli both in vitro and in vivo. As a first step toward understanding how hormonal and developmental factors regulate IGFBP-3 production, we are characterizing the human IGFBP-3 chromosomal gene and promoter. Southern analysis demonstrates a single copy of the IGFBP-3 gene in the human genome. This gene spans 8.9 kilobases; the protein-coding region is divided into four exons while a fifth exon contains the 3'-untranslated region. Primer extension studies locate the IGFBP-3 mRNA cap site 132 base pairs 5' to the ATG translation initiation codon. On the chromosomal gene, this cap site is located 30 base pairs 3' to the start of a TATA box and 97 base pairs 3' to a consensus GC upstream promoter element, an organization common to many eukaryotic promoters. When this potential IGFBP-3 promoter region is placed upstream to the chloramphenicol acetyltransferase reporter gene, it directs high-level production of chloramphenicol acetyltransferase in transfected COS-1 cells. These observations suggest an uncomplicated organization for the IGFBP-3 chromosomal gene and promoter in the human genome.
...
PMID:Insulin-like growth factor binding protein-3. Organization of the human chromosomal gene and demonstration of promoter activity. 169 33

Familial glucocorticoid resistance is a hypertensive, hyperandrogenic disorder characterized by increased serum cortisol concentrations in the absence of stigmata of Cushing's syndrome. Our previous studies of the first reported kindred showed a two- to threefold reduction in glucocorticoid receptor-ligand binding affinity in the propositus, and a lesser reduction in affinity in his mildly affected son and nephew. Glucocorticoid receptor cDNA from these three patients was amplified by polymerase chain reaction and sequenced. The cDNA nucleotide sequence was normal, except for nucleotide 2054, which substituted valine for aspartic acid at amino acid residue 641. The propositus was homozygous while the other relatives were heterozygous for the mutation. COS-7 monkey kidney cells were cotransfected with expression vectors for either wild type or Val 641-mutant receptors, together with the reporter plasmid pMMTV-CAT. Dexamethasone increased chloramphenicol acetyltransferase activity in cells expressing wild type receptor, but had no effect in cells expressing Val 641-mutant receptors, despite similar receptor concentrations, as indicated by Western blotting. The binding affinity for dexamethasone of the Val 641-mutant receptor was threefold lower than that of the wild type receptor. These results suggest that glucocorticoid resistance in this family is due to a point mutation in the steroid-binding domain of the glucocorticoid receptor.
...
PMID:Point mutation causing a single amino acid substitution in the hormone binding domain of the glucocorticoid receptor in familial glucocorticoid resistance. 170 18

Expression of prostate-specific antigen (PA) mRNA was tested at various time periods after incubation of the human prostate tumor cell line LNCaP with the synthetic androgen R1881. Androgen-stimulated expression was observed within 6 h after addition of R1881 to the cells. Run-on experiments with nuclei isolated from LNCaP cells showed that expression of the PA gene could be regulated by R1881 on the level of transcription. DNase I footprints of the promoter region of the PA gene (-320 to +12) with nuclear protein extracts from LNCaP cells showed at least four protected regions. The protected areas include the TATA-box, a GC-box sequence, and a sequence AGAACAgcaAGTGCT at position -170 to -156, which closely resembles the reverse complement of the consensus sequence GGTACAnnnTGTTCT for binding of the glucocorticoid receptor and the progesterone receptor. Fragments of the PA promoter region were cloned in front of the chloramphenicol acetyltransferase (CAT) reporter gene and cotransfected with an androgen receptor expression plasmid into COS cells in a transient expression assay. CAT activity of COS cells grown in the presence of 1 nM R1881 was compared to untreated controls. A 110-fold induction of CAT activity was found if a -1600 to +12 PA promoter fragment was used in the construct. By further deletion mapping of the PA promoter a minimal region (-320 to -155) was identified as being essential for androgen-regulated gene expression. Mutation of the sequence AGAACAgcaAGTGCT (at -170 to -156) to AAAAAAgcaAGTGCT almost completely abolished androgen inducibility of the reporter gene constructs. One or more copies of the sequence AGAACAgcaAGTGCT cloned in front of a thymidine kinase promoter-CAT reporter gene confers androgen regulation to the reporter gene. These findings provide strong evidence for transcription regulation of the PA gene by androgens via the sequence AGAACAgcaAGTGCT. Interestingly, in addition to the AGAACAgcaAGTGCT element, an upstream region (-539 to -320) is needed for optimal androgen inducibility of the PA promoter.
...
PMID:The promoter of the prostate-specific antigen gene contains a functional androgen responsive element. 172 87

Nuclear transport, phosphorylation, ligand binding, and degradation rate of the recombinant androgen receptor (AR) were analyzed in transfected COS cells in the presence of various steroids and antiandrogens. Transcriptional activation was assessed in CV1 cells by cotransfection with an androgen-responsive chloramphenicol acetyltransferase (CAT) reporter vector. Hormone binding specificity of recombinant AR was essentially identical to endogenous AR. AR localized in the nucleus in the presence of methyltrienolone (R1881, a synthetic androgen), dihydrotestosterone, testosterone, hydroxyflutamide, cyproterone acetate, estradiol, progesterone, and RU486. In the absence of hormone or with the antiandrogen, flutamide, AR remained largely in the cytoplasm with a perinuclear distribution. AR was degraded rapidly (t1/2 = 1 h) except in the presence of androgen (t1/2 = 6 h) which accounted for an apparent 2-4-fold androgen-induced increase in AR phosphorylation, indicating that AR phosphorylation was not enhanced by androgen. CAT activity was stimulated by R1881, dihydrotestosterone, testosterone, cyproterone acetate, estradiol, progesterone, and RU486 in a dose-dependent manner. The antiandrogens, flutamide and hydroxyflutamide, lacked agonist activity and inhibited R1881-induced activation of CAT and androgen stabilization of AR. Steroids and antiandrogens with moderate to low affinity for AR promoted both nuclear transport and transcriptional activation but only at high hormone concentrations. Hydroxyflutamide acted as a true antiandrogen since it lacked agonist activity and was an inhibitor of androgen-induced transcriptional activation.
...
PMID:Androgen receptor phosphorylation, turnover, nuclear transport, and transcriptional activation. Specificity for steroids and antihormones. 173 Jun 84

Reovirus S4 RNA codes for the dsRNA-binding polypeptide sigma 3, a major virion outer capsid component that also has translational effects in both infected and transfected mammalian cells. To compare the composition and properties of the three different serotypes of sigma 3, a DNA copy of the type 2 gene was cloned and sequenced. The total lengths (1196) and the sequences of leader (33 nucleotides) and trailer (66 nucleotides) regions are highly conserved among the three S4 serotypes. The type 1 and 3 S4 genes are highly related (77 mismatches). However, the type 2 gene contains many mismatches relative to the type 1 and 3 genes (260 and 270 positions, respectively). Most of the mismatches are third position changes, resulting in sigma 3 polypeptides that are 90% or more identical. Transient expression vectors, constructed by replacing the chloramphenicol acetyltransferase (CAT) gene in pRSVCAT with S4 DNA, were used to test the effects of polypeptide sigma 3 on CAT expression in cotransfected COS cells. Transfection with the correctly oriented DNAs resulted in synthesis of the corresponding sigma 3 polypeptides which enhanced CAT expression. The type 2 and type 3 S4 genes were considerably more stimulatory than type 1 when compared to CAT DNA alone. However, with all three serotypes the CAT activity was significantly higher in cells cotransfected with S4 DNA in the correct orientation as compared to the reverse arrangement.
...
PMID:Translational effects and sequence comparisons of the three serotypes of the reovirus S4 gene. 173 24

The effect of myristoylation on p27nef subcellular distribution and suppression of HIV-1 transcription was examined by transfecting COS-7 cells with plasmids expressing either myristoylated (pSVnef) or nonmyristolyated p27nef (pSVnefala2). Similar levels of myristoylated and nonmyristoylated p27nef were expressed with only the product of the pSVnef plasmid being myristoylated. Immuno-histochemical microscopy and radioimmunoprecipitation revealed myristolyated p27nef only in the membrane fraction while nonmyristolyated p27nef was found distributed between the nucleus and the cytosol fractions. The effect of myristoylation on p27nef suppression of HIV LTR controlled transcription was examined in transient transfected COS cells and in CEM human T-cell clones consituitively expressing either myristolyated or nonmyristolyated p27nef by cotransfecting with a chloramphenicol acetyltransferase (CAT) plasmid under control of the HIV-1 LTR. In both systems, myristoylated p27nef exhibited a 13- to 18-fold inhibition of basal CAT activity while the nonmyristolyated mutant and the same plasmid carrying the nef gene in a reverse orientation inhibited CAT activity one- to two-fold. These results confirm the cytoplasmic membrane localization of p27nef and establish that its subcellular targeting is dependent on covalently attached myristate. The data also provide further evidence that p27nef acts as a transcriptional suppressor and establishes for the first time that myristolyation is required for the full manifestation of this effect.
...
PMID:Effect of myristoylation on p27 nef subcellular distribution and suppression of HIV-LTR transcription. 173 44


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---