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)

To examine the role of nuclear retinoic acid (RA) receptors (RARs) in the regulation of squamous differentiation in normal human epidermal keratinocytes (NHEK), we analyzed binding activity, mRNA expression, and transcriptional activity of the endogenously expressed RARs. Specific RA-binding activity eluted from size-exclusion HPLC with an apparent mol wt of 50 kilodaltons and was predominantly (greater than 95%) associated with the NHEK nuclear cell fraction. This RAR-binding activity represented in part the expression of RAR alpha and RAR gamma genes, whose transcripts were expressed in similar abundance in undifferentiated NHEK. Differentiation resulted in lower mRNA expression of RAR alpha relative to the mRNA expression of RAR gamma. Treatment of NHEK cells with 10(-6) M RA did not induce expression of RAR beta mRNA. Similarly, three squamous cell carcinoma cell lines derived from human skin and oral cavity expressed RAR alpha and RAR gamma transcripts, but not RAR beta transcripts. Transfection of NHEK with chloramphenicol acetyltransferase (CAT) reporter plasmids indicated that the endogenously expressed RARs could activate transcription through the RAR beta response element in a concentration-dependent manner with doses of 10(-9) M RA and higher. CAT expression was not activated through TRE, a palindromic thyroid hormone response element with purported RA responsiveness. The competitive binding of benzoic acid derivatives of RA to RAR correlated with the ability of each analog to suppress mRNA expression of the squamous cell markers, involucrin, type I transglutaminase, and SQ37, and to activate transcription of the RAR beta response element-CAT reporter. These results demonstrate that the control of NHEK differentiation by RA is consistent with the interaction of the retinoid with RAR and the regulation of transcription by that ligand-receptor complex.
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PMID:Retinoic acid receptors as regulators of human epidermal keratinocyte differentiation. 131 2

Involucrin is one of the precursor proteins of keratinocyte cornified envelope. Although the formation of the cornified envelope is induced by tumor-promoting phorbol esters, the effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the involucrin gene expression remains unknown. We have isolated a 5'-upstream region of human involucrin gene and examined its TPA-dependent promoter activity. The involucrin upstream region with the untranslated first exon was connected to chloramphenicol acetyltransferase (CAT)-involucrin promoter expression vector (INV-CAT) and was transfected into fetal rat keratinizing epidermal (FRSK) cells. The INV-CAT-transfected FRSK cells showed considerable CAT activity that was significantly augmented by the treatment of cells with TPA. FRSK cells that were transfected with a reversely oriented 5'-upstream sequence revealed little CAT activity and did not respond to TPA. The effect of TPA was significantly inhibited by the protein kinase C inhibitor 1-(5-isoquinoline-sulfonyl)-2-methyl piperazine dihydrochloride (H-7). Other protein kinase C activators (1-oleoyl-2-acetylglycerol and mezerein) also induced the INV-CAT promoter activity, whereas 4-O-methyl phorbol myristate acetate, a very weak protein kinase C activator, had only a slight effect. Analysis of the nucleotide sequence of the 5'-upstream region detected several 5'-TGANTCAA-3' sequences that are highly conserved TPA-response elements (TRE). Cotransfection of both c-jun and c-fos expression vectors with the INV-CAT vector into FRSK cells resulted in increased CAT activity. Cotransfection of either the c-jun or c-fos vector singly with the INV-CAT vector into FRSK cells had negligible effects. Dexamethasone significantly inhibited the TPA-induced promoter activity in the INV-CAT-transfected FRSK cells. These results indicate that involucrin gene expression is positively controlled by TPA through the activation of the protein kinase C/TRE system.
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PMID:Analysis of the 5'-upstream promoter region of human involucrin gene: activation by 12-O-tetradecanoylphorbol-13-acetate. 838 Aug 29

Involucrin is one of the precursor proteins of keratinocyte cornified envelope that is formed beneath the inner surface of the cell membrane during terminal differentiation. Although involucrin is specifically expressed in the upper squamous cells of the epidermis, the precise regulatory mechanism of involucrin gene expression remains unknown. Transcriptional enhancer factor 1 (TEF-1), which binds to SV40 enhancer, is a nuclear protein expressed in various types of cells including keratinocytes. Immunohistochemical study has revealed that TEF-1 protein is highly expressed on the basal cell layer of the epidermis. To examine the possible regulatory mechanism of involucrin gene expression by TEF-1 protein, we analysed involucrin promoter activity of the INV-CAT vector, which was constructed by connecting the 5' upstream region of the involucrin gene (-801 bp upstream from the transcription start site and downstream including the untranslated first exon) to the chloramphenicol acetyltransferase (CAT) reporter gene. The INV-CAT vector was transfected to SV40-transformed human keratinocytes (SVHK). Cotransfection of the TEF-1 expression vector significantly repressed INV-CAT promoter activity in a dose-dependent manner. The repression was also observed by transfection of the GAL4-TEF-1 vector, which was constructed by replacement of the TEF-1 DNA binding domain by the GAL4 activator domain. This suggests that TEF-1-induced repression is due to interference/squelching of a limiting transcriptional intermediary factor that is essential for involucrin expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Repression of involucrin gene expression by transcriptional enhancer factor 1 (TEF-1). 855 86