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)

Collagen II, the major component of cartilage, is synthesized primarily by chondrocytes and by certain cells in the eye. Previously, we have studied the regulatory regions of the collagen II gene by DNA transfection assays (Horton, W., Miyashita, T., Kohno, K., and Yamada, Y. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 8864-8868). These studies show that both the promoter and an enhancer sequence in the first intron are required for high transcriptional activity in chondrocytes. These elements do not show significant activity in cells which do not synthesize collagen II, such as in muscle cells and fibroblasts. In this report, we have constructed plasmids containing various deletions of the promoter of the collagen II gene, fused to a reporter gene for chloramphenicol acetyltransferase (CAT) and transfected them into both chick embryonic fibroblasts and HeLa cells. We have found that silencer elements in the collagen II promoter region reduce CAT activity 11-fold in fibroblasts, while not affecting the enhancer-mediated transcription in chondrocytes. Deletions in the promoter showed that most of the silencing activity was localized in two sites, between -360 and -460 base pairs and between -620 and -700 base pairs. Furthermore, a fragment containing these two sequences in a thymidine kinase promoter CAT construct reduced the activity of the promoter in an orientation independent fashion. Sequence analysis revealed that the two silencer regions are homologous and contain consensus motifs for silencer elements found in other genes. Gel retardation experiments showed that nuclear factors from HeLa cells bind specifically to a DNA fragment containing the silencer, whereas chondrocyte nuclear extracts did not show any activity. Thus, our study indicates that the expression of the collagen II gene is controlled by both negative and positive elements to ensure that the gene is only expressed in suitable cells.
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PMID:Two silencers regulate the tissue-specific expression of the collagen II gene. 232 96

Type I collagen synthesis and deposition is generally indicative of irreversible damage in alcohol-induced cirrhosis in humans. However, in rodents, ethanol alone does not readily cause hepatic fibrosis. To determine whether this is because of a lack of ethanol-responsive elements, an artificial enhancer construct controlling rat type I collagen gene transcription was prepared in transgenic mice. The gene construct, ColCAT3.6, was a chimeric sequence containing the marker chloramphenicol acetyltransferase (CAT) gene linked to 3.5 kb of the rat alpha 1(I) 5'-flanking DNA, and 115 base pairs (bp) of transcribed collagen gene. Groups of transgenic mice were given 4 g/kg ethanol orally, twice daily for 4 weeks. As a positive control for hepatic fibrosis, transgenic mice were given intraperitoneal injections of CCl4, twice weekly for 4 weeks. Livers were assayed for CAT activity. Endogenous mouse collagen alpha 1(I) messenger RNA (mRNA) and transgene CAT mRNA were measured by RNase protection assays. Collagen synthesis in livers from the transgenic mice treated with ethanol were increased over controls, but the levels were not significantly different. Endogenous collagen alpha 1(I) steady-state mRNA levels in ethanol-treated mice were not significantly different compared with saline-treated controls. However, the transgene mRNA levels in ethanol-treated animals increased approximately 21-fold compared with saline-treated controls, as measured by RNase protection assays. Furthermore, the transgene product as measured by CAT activity in ethanol-treated mice was significantly increased threefold over saline-treated controls. We conclude that the 5'-flanking region of the rat alpha 1(I) collagen gene does contain regulatory elements that are strongly responsive to ethanol administration.
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PMID:A collagen enhancer-promoter construct in transgenic mice is markedly stimulated by ethanol administration. 859 57

Administration of TGF-beta, a fibrogenic inflammatory growth factor, promotes fibrosis and scarring. Dexamethasone, an anti-inflammatory steroid, inhibits wound healing and reduces fibrosis. The current studies were initiated to determine whether the co-administration of dexamethasone was able to abrogate the fibrogenic effect of TGF-beta. Polyvinyl alcohol sponges were implanted subcutaneously on the abdominal area of rats and directly injected with vehicle, dexamethasone, TGF-beta, or dexamethasone plus TGF-beta. Dexamethasone was able to block the fibrogenic effect of TGF-beta. Collagen and noncollagen protein synthesis was measured as a function of TGF-beta or dexamethasone concentrations in fibroblasts isolated from granulation tissue. Addition of dexamethasone to cultures treated simultaneously with TGF-beta blocked the fibrogenic response of TGF-beta. To study the molecular regulation of collagen gene expression by TGF-beta or dexamethasone, fibroblasts derived from granulation tissue were stably transfected with the ColCat 3.6 plasmid, which contains the rat pro alpha1(I) collagen promoter linked to the chloramphenicol acetyltransferase (CAT) gene. Dexamethasone decreased CAT activity whereas TGF-beta increased the activity of this reporter gene. The increase in CAT activity observed with TGF-beta treatment was significantly decreased when dexamethasone was added to the cultures, although CAT activity did not return to control level. Since collagen synthesis in fibroblasts treated simultaneously with dexamethasone and TGF-beta1 was found to be the same as that of untreated samples, the data indicate that there is a dexamethasone-mediated posttranscriptional regulation of pro alpha1(I) collagen mRNA. These studies demonstrate that at the in vivo level, the cellular level, and the molecular level, dexamethasone is able to block the fibrogenic effect of TGF-beta.
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PMID:Dexamethasone abrogates the fibrogenic effect of transforming growth factor-beta in rat granuloma and granulation tissue fibroblasts. 903 26