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)

In an attempt to understand the molecular mechanism regulating the expression of the gene coding for human hepatocyte growth factor-like protein/macrophage stimulating protein (HGFL), our laboratory has isolated and characterized approximately 4200 bp of the 5'-flanking region of the HGFL gene. To determine the location of sites which may be critical for the function of the HGFL gene promoter, we constructed a series of hybrid genes containing serial deletions of this region attached to the coding sequences for chloramphenicol acetyltransferase. Expression of these chimeric plasmids was examined by transient transfection of HepG2 and 293 cells. Our results suggest that the transcriptional activity of the HGFL promoter is modulated in HepG2 cells by one positive element at position -135 to -105 (-135/-105). In contrast, only background levels of chloramphenicol acetyltransferase expression have been detected in 293 cells. The -135/-105 region appears to bind a liver-specific transcription factor essential for expression of this gene. Gel mobility shift experiments with antibodies against hepatocyte nuclear factor-4 (HNF-4) and transactivation of the HGFL promoter by a HNF-4 cDNA expression vector suggest that HNF-4 binds to the -135/-105 region and is responsible for the liver-specific expression of HGFL.
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PMID:Hepatocyte nuclear factor-4 is responsible for the liver-specific expression of the gene coding for hepatocyte growth factor-like protein. 862 50

RON (recepteur d'origine nantais) is a receptor tyrosine kinase expressed in murine peritoneal resident macrophages and activated by macrophage-stimulating protein (MSP). The objectives of this investigation were to study the RON expression in exudate macrophages and the mechanisms by which RON inhibits inducible nitric oxide synthase (iNOS) expression induced by LPS and IFN-gamma. We found that mouse peritoneal resident and Con A-elicited macrophages collected on day 3 or day 5 express RON. Acute exudate macrophages collected on day 1 did not express RON. Activation of RON inhibited LPS- and IFN-gamma-induced macrophage nitric oxide production and iNOS mRNA accumulation. Similar inhibition was observed also in Raw264.7 macrophage cell lines transfected with human RON cDNA. In these cells, MSP induced RON phosphorylation concomitant with reduced iNOS mRNA expression and protein synthesis. Further, we show that activated RON inhibited the iNOS gene transcription activity as assessed by chloramphenicol acetyltransferase activity in Raw264.7 cells expressing RON. Wortmannin, a specific inhibitor of phosphatidylinositol-3 (PI-3) kinase, prevented the inhibitory effect of RON on the iNOS gene promoter activity and on the nitric oxide production induced by LPS and IFN-gamma. These effects were confirmed further by introducing a dominant-inhibitory PI-3 kinase p85 subunit in RON-expressing Raw264.7 cells. Taken together, our results suggest that RON is expressed in peritoneal macrophages at later stages of inflammation. Activation of RON by MSP in mature exudate macrophages inhibits LPS- and IFN-gamma-induced iNOS synthesis. PI-3 kinase is an important effector molecule required for RON-mediated inhibition of iNOS expression in macrophages.
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PMID:Activation of the RON receptor tyrosine kinase inhibits inducible nitric oxide synthase (iNOS) expression by murine peritoneal exudate macrophages: phosphatidylinositol-3 kinase is required for RON-mediated inhibition of iNOS expression. 979 31

Previous studies from our laboratory demonstrated that the hepatocyte-specific transcriptional activity of the hepatocyte growth factor-like protein/macrophage stimulating protein (HGFL) promoter is modulated in HepG2 cells by the first 135 base pairs (bp) upstream of the HGFL transcriptional start site. Gel mobility shift and transactivation assays demonstrated that hepatocyte nuclear factor-4 (HNF-4) binds to this region and is responsible, in part, for the liver-specific expression of this gene in HepG2 cells. In an attempt to understand the in vivo mechanism regulating the expression of HGFL, a series of transgenic mice were generated that contained four different regions upstream of the HGFL promoter attached to the coding sequences for chloramphenicol acetyltransferase (CAT). Interestingly, upstream promoter sequences, containing as little as 104 bp upstream of the translational start site, were able to drive reporter expression and protein production specifically in kidney and liver tissue. Strikingly, when the first exon and intron of the HGFL gene was inserted downstream of the 135 bp promoter element, only liver-specific expression was observed. These studies indicate that short sequences upstream of HGFL can drive efficient expression in kidney and liver tissue, and that sequences in the first intron of the HGFL gene contain regulatory elements that direct kidney-specific transcriptional repression in vivo and aid in the proper recapitulation of HGFL expression in mice.
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PMID:Cis-acting elements in the hepatocyte growth factor-like protein gene regulate kidney and liver-specific expression in mice. 1294 Nov 57