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)

Release of prolactin from both normal pituitary cells and rat pituitary tumor (GH) cells is an osmotic process that is dependent upon chloride. The long term growth rate of GH-cells in medium in which chloride was exchanged with isethionate was completely normal, but, by 48 h, isethionate substitution resulted in a 70% decrease in the concentration of internal and secreted prolactin. Isethionate caused a much smaller reduction in growth hormone production (less than 20%). These results suggest that exchange of chloride with isethionate is inhibiting the synthesis of prolactin. Reduction of intracellular levels of prolactin in cells grown in isethionate-containing medium was evident by 30 h, and the level of prolactin was reduced 92% at 96 h. This reduction in the internal concentrations of prolactin was reversed when the cells were returned to normal medium containing chloride with a t1/2 of 48 h. Addition of epidermal growth factor and the calcium channel agonist BAY K 8644 to cells in medium containing chloride increased internal prolactin by 400%, and isethionate exchange reduced the response by 85%. To confirm that isethionate exchange was inhibiting the synthesis of prolactin, mRNA concentrations for prolactin and actin were determined. Both basal and hormone-stimulated levels of prolactin mRNA were reduced 70 to 90% by isethionate exchange, while actin mRNA levels did not change. To determine whether the effect of isethionate was at the level of gene transcription, GH-cells were transfected with a prolactin-chloramphenicol acetyltransferase fusion gene and chloramphenicol acetyltransferase expression was assessed using cells in chloride and isethionate-containing media. Both basal and hormone-stimulated synthesis of chloramphenicol acetyltransferase driven by the prolactin promoter was inhibited by isethionate exchange. These studies demonstrate that exchange of medium chloride with isethionate inhibits the synthesis of prolactin at the level of transcription.
...
PMID:Prolactin synthesis in cultured pituitary cells is chloride-dependent. 246 Apr 42

The possible role of the catalytic subunit of the cAMP-dependent protein kinase in mediating the regulation of prolactin gene transcription has been investigated through the use of a synthetic gene encoding the heat-stable inhibitor of the cAMP-dependent protein kinase. To assess the effects of protein kinase inhibitor expression on cAMP induction of prolactin gene transcription, a marker gene containing the rat prolactin promoter and adjacent 5'-flanking sequences linked to the bacterial chloramphenicol acetyltransferase gene was cotransfected with a protein kinase inhibitor-expression vector. The results demonstrate that the protein kinase inhibitor-expression vector reduced both basal and cAMP-stimulated expression of the cotransfected prolactin-chloramphenicol acetyltransferase gene. A mutant protein kinase inhibitor-expression vector, coding for an inactive inhibitor protein, did not inhibit basal or cAMP-stimulated prolactin gene transcription. Furthermore, the protein kinase inhibitor-expression vector did not inhibit zinc induction of the metallothionein promoter. Analysis of protein kinase activity in transfected cells demonstrated that the protein kinase inhibitor expression vector reduced cAMP-dependent protein kinase activity but did not reduce protein kinase C activity. Nuclease protection experiments confirmed that the effects of the inhibitor vector involved changes in correctly initiated transcripts produced from the prolactin promoter. Surprisingly, the protein kinase inhibitor-expression vector reduced the effects of several different agents including epidermal growth factor, thyrotropin-releasing hormone, phorbol esters, and estrogen on prolactin gene expression to the same extent as it altered cAMP effects.
...
PMID:A protein kinase inhibitor gene reduces both basal and multihormone-stimulated prolactin gene transcription. 253 42

We have detected hormone response elements in the promoter region of the rat beta-casein gene that confer the synergistic action of prolactin and glucocorticoid hormones upon transcription of chimeric gene constructs. A 2800-base-pair (bp) rat beta-casein gene fragment containing 2300 bp of 5' flanking sequence was placed in front of a chloramphenicol acetyltransferase (CAT) reporter gene and stably transfected into the mouse mammary epithelial cell line HC11. Addition of prolactin or dexamethasone alone was sufficient for a modest induction of the fusion gene. The simultaneous presence of both hormones produced a strongly synergistic effect, which did not require the presence of insulin. Induction of the beta-casein-CAT gene was only observed in stably transfected confluent cell cultures. Analysis of a 5' deletion series of the beta-casein-CAT gene construct revealed a stepwise loss of hormone inducibility; 285 bp of 5' flanking sequence was sufficient to mediate the synergistic action of lactogenic hormones on expression. The response was reduced by half when compared with the construct containing 2300 bp of the 5' flanking region. Synergistic inducibility further decreased in deletion mutants between -285 and -265 and was completely abolished between -180 and -170. Thus, the 5' flanking region between -285 and -170 contains cis-acting sequences, which are required for mediating the effect of prolactin and dexamethasone.
...
PMID:Prolactin and glucocorticoid hormones synergistically induce expression of transfected rat beta-casein gene promoter constructs in a mammary epithelial cell line. 264 93

A 1-kilobase DNA fragment containing the promoter of the bovine prolactin gene was fused to the chloramphenicol acetyltransferase gene and the activity of the promoter was assayed by transfection of the fusion gene into COS-1, HeLa, and GH3 cells. Transcription of the chloramphenicol acetyltransferase gene driven by the prolactin promoter was detected only in GH3 cells, a rat pituitary tumor cell line. Epidermal growth factor and thyroid releasing hormone produced a stimulation of transcription, and the synthetic glucocorticoid hormone dexamethasone effected an inhibition of transcription from the prolactin promoter. None of these factors significantly affected transcription of the chloramphenicol acetyltransferase gene fused to the Rous sarcoma virus promoter. Deletion of all but 250 base pairs of bovine prolactin 5'-flanking DNA had no effect, indicating that the signals sufficient for both stimulation and inhibition of transcription reside in close proximity to the promoter.
...
PMID:Hormonal regulation of the bovine prolactin promoter in rat pituitary tumor cells. 299 68

The 5'-flanking region of the rat prolactin gene contains two DNase I-hypersensitive (HS) sites. We used gene transfer experiments to determine the nucleotide (nt) sequences within and around these two HS sites that may contain the information necessary for regulation of prolactin gene expression by estrogens and glucocorticoids. A chimeric gene construct (pPRL.CAT) was prepared by covalently linking the sequence of the rat prolactin gene to the bacterial chloramphenicol acetyltransferase-coding gene, cat. Rat GH3 cells were transfected with pPRL.CAT and six mutants that possess deletions within and around the two HS sites. Incubation of such transfectants with estrogen or dexamethasone indicated the existence of two functionally important elements within the 5'-flanking region of the rat prolactin gene. The element required for estrogen up-regulation of the prolactin gene is located between nt residues -1530 through -1950. The glucocorticoid down-regulatory element is located between nt -200 and +75.
...
PMID:Two elements of the rat prolactin 5' flanking region are required for its regulation by estrogen and glucocorticoids. 322 19

We have used MCF-7, the human breast cancer cell line, which is estrogen receptor-positive, and the HeLa cell line, which is estrogen receptor-negative, to study the mechanisms by which estrogen induces prolactin gene transcription. A series of plasmids were constructed which direct the expression of the easily assayed bacterial enzyme chloramphenicol acetyltransferase. We have used these recombinants to show that the estrogen-responsive DNA element (ERE) required for the estrogenic regulation of the rat prolactin gene is functional in MCF-7 cells but not in HeLa cells. Specifically, in MCF-7 cells this element enhances the level of gene activity after estrogen treatment both from its own promoter and from a heterologous (simian virus 40) promoter. Results of these studies also show that in HeLa cells the ERE can mediate estrogenic regulation if cotransfected with a plasmid that can synthesize estrogen receptor.
...
PMID:An estrogen-responsive element from the 5'-flanking region of the rat prolactin gene functions in MCF-7 but not in HeLa cells. 322 23

The DNA sequences which interact with the estrogen receptor and which mediate the estrogenic regulation of prolactin gene transcription have been investigated by the use of receptor-DNA-binding experiments and gene transfer studies. Nitrocellulose filter binding assays using highly purified estrogen receptor and cloned fragments of the 5'-flanking region of the rat prolactin gene demonstrate that the receptor selectively binds to DNA sequences located between nucleotides -1713 and -1532 with respect to the transcription initiation site. The binding of the estrogen receptor to this region of the prolactin gene was strongly dependent on receptor concentration, suggesting that receptor dimers may be important in DNA binding. These data demonstrate that the selective binding of purified estrogen receptor to specific sequences of the rat prolactin gene is an intrinsic property of the receptor and is not due to the interaction of receptor with other proteins. The role of specific prolactin gene sequences in mediating the estrogenic regulation of prolactin gene transcription was confirmed by the use of prolactin-chloramphenicol acetyltransferase fusion genes. These studies demonstrated that sequences upstream of position -1532 are required for estrogen responsiveness. Furthermore, the region of the prolactin gene at -1713 to -1495 was able to confer estrogen responsiveness on the thymidine kinase promoter. Exonuclease III protection experiments further localized the receptor-binding sequences to positions -1587 to -1563. Comparison of the nucleotide sequence of the region of the prolactin gene which binds the estrogen receptor with the sequence of other estrogen-responsive genes suggested the presence of the conserved sequence [sequence in text], which shows similarity to sequences thought to mediate glucocorticoid receptor effects on transcription.
...
PMID:Identification of an estrogen-responsive element from the 5'-flanking region of the rat prolactin gene. 348 34

We have investigated the ability of a constitutively active Gq-alpha mutant, Q209L-alpha q, to regulate target gene expression. Transient expression in GH3 pituitary cells of a rat proximal prolactin promoter-chloramphenicol acetyltransferase construct (-187)PRL-CAT, was stimulated by co-expression of Q209L alpha q, but not by wild-type alpha q. Q209L-alpha q stimulated expression of constructs driven by promoters for either rat prolactin or growth hormone, but not of a control construct driven by the thymidine kinase promoter. Thus, transcriptional effects of alpha q are specific both for the activated state of this G-alpha subunit and the promoter examined. Since both the prolactin and growth hormone promoters are activated by the pituitary cell-specific transcription factor Pit-1, we examined whether a Pit-1 binding site could direct a response to Q209L-alpha q. Two copies of prolactin promoter Pit-1 binding site 1P conferred upon a heterologous metallothionein promoter a response to Q209L-alpha q, implying an involvement of this site in the transcriptional action of Q209L-alpha q on the prolactin promoter. The phorbol ester activator of protein kinase C, 12-O-tetradecanoylphorbol-13-acetate, stimulated (-187)PRL-CAT activity, but opposed the action of Q209L-alpha q on activity of this PRL-CAT construct. Q209L-alpha q stimulation of (-187)PRL-CAT activity was inhibited by co-expression of a dominant negative Raf mutant, Raf-C4, but not by a point mutant of Raf-C4 with reduced inhibitory properties. These results imply that activated alpha q subunits can stimulate prolactin promoter activity via a pathway that involves a Pit-1 DNA binding site(s), is opposed by protein kinase C, and is mediated by a pathway in which Raf-1 kinase plays a role.
...
PMID:Constitutively active Gq-alpha stimulates prolactin promoter activity via a pathway involving Raf activity. 748 29

Insulin increases expression of somatostatin-chloramphenicol acetyltransferase (CAT) constructs 10-fold and thymidine kinase-CAT constructs 5-fold in GH4 cells. These responses are similar to our previously reported data on insulin-increased prolactin-CAT expression. They are also observed in HeLa cells and are thus not cell type specific. The evidence suggests that the insulin responsiveness of these genes is mediated by an Ets-related transcription factor. First, linker-scanning mutations and/or deletions of the prolactin, somatostatin, and thymidine kinase promoters suggest that their insulin responsiveness is mediated by the sequence CGGA. This sequence is identical with the response element of the Ets-related transcription factors. Second, CGGA-containing sequences placed at -88 in the delta MTV-CAT reporter plasmid conferred insulin responsiveness to the mammary tumor virus promoter. Third, expression of the DNA-binding domain of c-Ets-2, which acts by blocking effects mediated by Ets-related transcription factors, inhibits the response of these promoters to insulin. Finally, the Ets-related proteins Sap and Elk-1 bind to the prolactin, somatostatin, and thymidine kinase insulin-response elements. An Ets-like element was found in all insulin-sensitive promoters examined and may serve a similar function in those promoters.
...
PMID:A consensus insulin response element is activated by an Ets-related transcription factor. 749 46

The physiological role of tenascin in vivo has remained obscure. Although tenascin is regulated in a stage and tissue-dependent manner, knock-out mice appear normal. When tenascin expression was examined in the normal adult mouse mammary gland, little or none was present during lactation, when epithelial cells actively synthesize and secrete milk proteins in an extracellular matrix/lactogenic hormone-dependent manner. In contrast, tenascin was prominently expressed during involution, a stage characterized by the degradation of the extracellular matrix and the subsequent loss of milk production. Studies with mammary cell lines indicated that tenascin expression was high on plastic, but was suppressed in the presence of the laminin-rich, Engelbreth-Holm-Swarm (EHS) tumour biomatrix. When exogenous tenascin was added together with EHS to mammary epithelial cells, beta-casein protein synthesis and steady-state mRNA levels were inhibited in a concentration-dependent manner. Moreover, this inhibition by tenascin could be segregated from its effects on cell morphology. Using two beta-casein promoter constructs attached to the chloramphenicol acetyltransferase reporter gene we showed that tenascin selectively suppressed extracellular matrix/prolactin-dependent transcription of the beta-casein gene in three-dimensional cultures. Finally, we mapped the active regions within the fibronectin type III repeat region of the tenascin molecule that are capable of inhibiting beta-casein protein synthesis. Our data are consistent with a model where both the loss of a laminin-rich basement membrane by extracellular matrix-degrading enzymes and the induction of tenascin contribute to the loss of tissue-specific gene expression and thus the involuting process.
...
PMID:Tenascin-C inhibits extracellular matrix-dependent gene expression in mammary epithelial cells. Localization of active regions using recombinant tenascin fragments. 753 36


<< Previous 1 2 3 4 Next >>

---