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

A proinflammatory cytokine cascade, including IL-1 alpha, IL-1 beta, TNF-alpha, IL-6, and IL-8, is activated in response to infection or immunologic insult. Besides their immunologic effects, several of these mediators stimulate bone resorption and inhibit bone formation. Osteocalcin, the most abundant noncollagenous protein present in bone, is an osteoblast-specific product whose production closely correlates with bone formation, and which has also been implicated in control of bone resorption. IL-1 and TNF have previously been shown to down-regulate osteocalcin production in vitro and in vivo, although the mechanism of this inhibition is unknown. In the present studies, IL-1 beta and TNF-alpha both inhibited 1,25-dihydroxyvitamin D3-stimulated production of osteocalcin protein and mRNA by ROS 17/2.8 osteosarcoma cells, whereas IL-6 had no effect on protein and only weakly inhibited mRNA. To determine if down-regulation was exerted at the transcriptional level, an osteocalcin promoter-chloramphenicol acetyltransferase (CAT) fusion gene was constructed (PHOC-CAT). After transient transfection of PHOC-CAT into ROS 17/2.8 osteosarcoma cells, reporter CAT activity was up-regulated by vitamin D at concentrations above 10(-12) M. In screening studies, TNF-alpha (-57%) and IL-6 (-37%) inhibited vitamin D-stimulated osteocalcin transcription, whereas IL-1 alpha, IL-1 beta, and IL-8 had no effect. Other immune cytokines and growth factors, including IL-2, IL-3, IL-7, and M-CSF, also failed to regulate osteocalcin transcription. Despite their lack of promoter regulation, IL-1 alpha and IL-1 beta also stimulated PGE2 production by ROS 17/2.8, further confirming the ability of the host cell to respond to these mediators. In dose-response experiments, down-regulation by TNF-alpha was significant at concentrations as low as 0.14 pM (0.1 U/ml), whereas approximately 10(4)-fold higher concentration of IL-6 was required to exert a similar effect. TNF-alpha-mediated down-regulation was unaffected by indomethacin. These data demonstrate that of these cytokines, TNF-alpha alone potently down-regulates osteocalcin promoter function, whereas IL-1 acts post-transcriptionally, possibly by reducing mRNA stability. Heterogeneity therefore exists among the proinflammatory cytokines with respect to the level at which control of osteocalcin expression is exerted.
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PMID:Proinflammatory cytokines tumor necrosis factor-alpha and IL-6, but not IL-1, down-regulate the osteocalcin gene promoter. 130 41

Granulocyte-macrophage colony stimulating factor (GM-CSF) stimulates the growth and differentiation of human hematopoietic progenitor cells by activating transcription of specific genes. The mechanism by which binding of GM-CSF to its receptor stimulates gene expression remains unknown. To examine this process in more detail, we have transfected human monocytic leukemia cells U937 with a plasmid containing an AP-1 enhancer element and a chloramphenicol acetyltransferase recorder gene and treated them with GM-CSF. We find that GM-CSF stimulates a 2-3-fold increase in chloramphenicol acetyltransferase activity over a concentration range 1-1,000 units/ml. Northern and Western blot analysis demonstrates that the mechanism by which GM-CSF stimulates AP-1 enhancer activity involves increases in c-jun and c-fos mRNA levels, and increases in Jun protein. In a similar fashion the treatment of normal human monocytes with GM-CSF also induced increases in total cellular c-jun. Because protein kinase C plays a crucial role in activating c-jun transcription we examined the role of this enzyme in mediating the effects of GM-CSF. Treatment of U937 cells with inhibitors of protein kinase C including staurosporine 10 nM and H-7 50 microM, or down-regulation of protein kinase C by phorbol ester pretreatment blocks the induction of c-jun by GM-CSF. However, HA which does not block protein kinase C had no effect on GM-CSF stimulation of c-jun RNA levels. In addition, GM-CSF treatment causes the rapid translocation of protein kinase C to the particulate fraction which was maximal by 5 min and returned to base line by 80 min. These data suggest that the binding of GM-CSF to its receptor stimulates increases in c-jun mRNA and protein and activates AP-1 enhancer activity. These effects may be at least in part mediated by activation of protein kinase C.
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PMID:Regulation of c-jun expression and AP-1 enhancer activity by granulocyte-macrophage colony-stimulating factor. 190 Aug 39

The macrophage colony-stimulating factor (M-CSF) is required for the growth and differentiation of mononuclear phagocytes. Previous studies have demonstrated that tumor necrosis factor (TNF) induces transcription of the M-CSF gene in human myeloid cells. The present work examined the effects of TNF on cis-acting elements in the M-CSF promoter. Deleted forms of the M-CSF promoter were linked to the chloramphenicol acetyltransferase (CAT) gene and transfected by electroporation into HL-60 promyelocytic leukemia cells. The results demonstrate that an enhancer responsive to TNF stimulation is located between positions -406 and -344 upstream to the transcription start site. The fragment from positions -419 to -304 was cloned 5' to the heterologous thymidine kinase (TK) promoter and linked to the CAT gene. Both orientations of this fragment enhanced TK-promoter activity in TNF-treated HL-60 cells. The results of gel mobility shift assays with the -419 to -304 fragment demonstrate binding of a constitutive nuclear protein. A TNF-inducible protein also bound to this fragment and resulted in a different mobility pattern. Binding of the TNF-induced nuclear protein to the -419 to -304 fragment was inhibited by an oligonucleotide containing the nuclear factor-kappa B (NF-kappa B) consensus sequence. DNA footprinting demonstrated protection of an NF-kappa B binding site at positions -377 to -368. Methylation interference assays showed that the TNF-induced protein made contact points with guanine residues in the same NF-kappa B sequence. Taken together, the findings provide evidence for involvement of an NF-kappa B-like factor in transcriptional regulation of the M-CSF gene.
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PMID:Involvement of a nuclear factor-kappa B-like protein in induction of the macrophage colony-stimulating factor gene by tumor necrosis factor. 191 81

Four lines of transgenic mice containing the HIV LTR linked to the bacterial gene encoding chloramphenicol acetyltransferase (CAT) were constructed. In each line, a characteristic tissue pattern of CAT expression was observed with detectable levels present in the eye, heart, spleen, thymus, and tail. Low levels of CAT were present in circulating lymphocytes, but CAT activity in these cells could be augmented following treatment with the mitogen phytohemagglutinin (PHA). Likewise, CAT expression was present at only low levels in circulating monocytes, but higher levels of CAT were observed in macrophages grown in the presence of various cytokines (CSF-1, GM-CSF, IL-1 alpha, IL-4, and IL-2). Furthermore, Langerhans cells recovered from skin showed higher levels of CAT activity than those observed in other cells of monocyte-macrophage lineage. These results indicate that LTR-CAT expression in cells of monocyte-macrophage lineage may increase in proportion to the degree of differentiation of these cells. These animals may be useful in the study of cell-specific determinants of LTR-directed gene activity and may serve to identify exogenous cofactors that promote the progression of HIV-related disease in vivo.
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PMID:The human immunodeficiency virus long terminal repeat is preferentially expressed in Langerhans cells in transgenic mice. 254 45

Colony-stimulating factors (CSFs) are glycoproteins that stimulate the growth of hematopoietic progenitors and enhance the functional activity of mature effector cells. Human granulocyte/macrophage colony-stimulating factor (GM-CSF) is a 22-kDa glycoprotein that stimulates the growth of myeloid and erythroid progenitors in vitro and increases the responsiveness of neutrophils, monocytes, and eosinophils to physiologic stimuli. Elucidation of the cell and tissue sources of CSFs, as well as study of their regulation of expression, is required to understand their role in physiologic and pathophysiologic states. An extensive survey of normal and neoplastic human tissues did not reveal constitutive production of detectable levels of GM-CSF mRNA in any of the 64 samples studied. Antigen- or lectin-activated T lymphocytes have been shown to produce GM-CSF; therefore, to elucidate the genetic sequences required, we constructed recombinant plasmids containing 5' flanking DNA of the GM-CSF gene linked to the marker chloramphenicol acetyltransferase gene. The recombinant constructs were transfected into a human T-cell leukemia virus type I (HTLV)-infected T-lymphoblast cell line that can be stimulated to produce high levels of GM-CSF. We show here that the 5' flanking sequences of the GM-CSF gene can direct increased expression of the chloramphenicol acetyltransferase gene in activated T-lymphoblast cells.
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PMID:Regulation of expression of human granulocyte/macrophage colony-stimulating factor. 349 Jun 69