Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transcription of the mouse vas deferens protein (MVDP) gene, a member of the aldo-keto reductase superfamily, is stimulated by androgens via the androgen responsive element (ARE) located in the proximal promoter (-111 to -97). We investigated interaction between androgens and the protein kinase C (PKC) signalling pathway. Transcriptional regulation was determined by analysis of chloramphenicol acetyltransferase (CAT). T47D cells were transiently transfected with 5' flanking MVDP DNA promoter sequences (-1804 to +41; -510 to +41 and -121 to +41) fused to the reporter (CAT) gene. Androgen-induced transcriptional activity can be enhanced from 6 (1.8 and 0.5 kb MVDP-CAT constructs) to 18 fold (0.16 kb MVDP-CAT construct), in a time and dose-dependent manner, by the PKC activator 12-o-tetradecanoylphorbol-13 acetate (TPA). A mutation in the proximal ARE abolished both androgen and TPA-dependent gene enhancement. TPA influenced minimally MMTV promoter in T47D cells and MVDP promoter in CV1 cells suggesting that the effects of the PKC activator are probably promoter and cell-specific. In contrast, activation of protein kinase A (PKA) via addition of dibutyryl-cAMP (db-cAMP) reduced androgen induction of the MVDP gene.
 ...
PMID:Protein kinase C pathway potentiates androgen-mediated gene expression of the mouse vas deferens specific aldose reductase-like protein (MVDP). 902 27

Androgen regulation of androgen receptor (AR) expression has been observed in a variety of tissues, generally as inhibition, and is thought to attenuate cellular responses to androgen. AR is expressed in osteoblasts, the bone-forming cell, suggesting direct actions of androgens on bone. Here we characterized the effect of androgen exposure on AR gene expression in human osteoblastic SaOS-2 and U-2 OS cells. Treatment of osteoblastic cells with the nonaromatizable androgen 5alpha-dihydrotestosterone increased AR steady state messenger RNA levels in a time- and dose-dependent fashion. Reporter assays with 2.3 kilobases of the proximal 5'-flanking region of the human AR promoter linked to the chloramphenicol acetyltransferase gene in transfected cultures showed that up-regulation of AR promoter activity by androgen was time and dose dependent. Treatment with other steroid hormones, including progesterone, 17beta-estradiol, and dexamethasone, was without effect. The antiandrogen hydroxyflutamide completely antagonized androgen up-regulation. Thus, in contrast to many other androgen target tissues, androgen exposure increases steady state AR messenger RNA levels in osteoblasts. This regulation occurs at least partially at the level of transcription, is mediated by the 5'-promoter region of the AR gene, and is dependent on functional AR. These results suggest that physiological concentrations of androgens have significant effects on AR expression in skeletal tissue.
 ...
PMID:Transcriptional up-regulation of the human androgen receptor by androgen in bone cells. 916 14

Androgen receptor (AR) plays a key role in cell growth both in the normal prostate and in prostate cancer. Androgen ablation and prolonged antiandrogen therapy can give rise to AR-dependent prostate tumors, which nonetheless can grow in the androgen-deprived milieu. Here we describe the ribozyme approach to selectively degrading the AR mRNA and thereby inhibiting AR function. A trans-acting hammerhead ribozyme was designed to cleave the rat AR mRNA at the position +1827/ 1828, a region predicted to be minimally involved in generating stable secondary structures. Using AR mRNA fragments as substrates, it was established that this ribozyme can specifically cleave the RNA target in a sequence-specific manner. Kinetic experiments determined a Km for the substrate of 77 nM and a kcat/Km value of 1.8 x 10(7) M(-1) x min(-1), suggesting a catalytic efficiency similar to that of protein enzymes such as the relatively nonspecific ribonuclease A and a sequence-specific endonuclease EcoRI. Transient cotransfections of prostate-derived PC3 cells with three plasmids, an AR-inducible chloramphenicol acetyltransferase (CAT) reporter, an AR expression vector, and a ribozyme expression vector, showed that the ribozyme was capable of reducing the functional activity of AR. At an equimolar ratio of the AR expression plasmid to ribozyme expression plasmid, androgen-inducible CAT activity was inhibited 70%. Similar extents of inhibition were also observed at the cellular mRNA level using ribonuclease protection assays, indicating that the ribozyme functioned as an AR mRNA cleaving enzyme in cellulo. Immunocytochemical examination revealed a decline of AR immunoreactivity in ribozyme-transfected cells. In addition, no morphologically detectable cellular abnormalities were associated with ribozyme expression, indicating the absence of deleterious side effects. These results offer a new avenue for the control of AR function and cell growth, especially in the case of androgen-resistant, but AR-dependent, prostate cancer cells.
 ...
PMID:Catalytic cleavage of the androgen receptor messenger RNA and functional inhibition of androgen receptor activity by a hammerhead ribozyme. 977 79

The MVDP (mouse vas deferens protein) gene, which encodes an aldose reductase-like enzyme, is mainly expressed in vas deferens epithelium and adrenal cortex. Vas deferens MVDP gene transcription was known to be under androgenic control, we now have evidence for androgen and probable ACTH responsiveness of the MVDP gene in the adrenal. To analyze the role of potential regulatory regions in hormonal, developmental, and tissue-specific aspects of MVDP regulation, we generated transgenic mice harboring MVDP-CAT fusion genes. The constructs carried either -1.8 or -0.5 kb 5'-flanking sequence attached to the chloramphenicol acetyltransferase gene in presence or absence of a 3.5-kb intragenic fragment in a downstream position. We show that at least two regions ensure proper gene regulation in vivo. The first, located within the 1.8-kb promoter fragment, directs tissue specificity; positive elements necessary for vas deferens and adrenal expression lay within positions -1804 to -510 and -510 to +41, respectively. The second, located within the 3.5-kb intragenic fragment spanning intron 1 to intron 2, increases percentage of expressing lines and behaves as a vas deferens-specific enhancer. Hormonal and developmental control of transgenes closely parallel endogenous gene regulation. Androgen and ACTH responsiveness in adrenals is conferred by 0.5-kb promoter, whereas in vas deferens, full androgenic response of the 1.8-kb promoter required the 3.5-kb intragenic fragment. Thus, vas deferens and adrenals use distinct cis-acting elements to direct and regulate the expression of the MVDP gene.
 ...
PMID:5'-flanking and intragenic sequences confer androgenic and developmental regulation of mouse aldose reductase-like gene in vas deferens and adrenal in transgenic mice. 1006 61


<< Previous 1 2