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)

One remarkable genetic feature of the class I MHC genes is their unparalleled degree of genetic polymorphism and diversity. The polymorphism is reflected by the fact that multiple loci encode class I molecules, and for each locus there are multiple alleles. In the course of investigating the regulation of HLA-A and HLA-B mRNA in human colorectal carcinoma cell lines, we have noticed a noncoordinate expression of the HLA mRNA in some of these cell lines. This observation prompted us to make use of these cell lines to study the locus-specific transcriptional regulation of HLA genes. Bandshift and footprint assays revealed at least three distinct and independent DNA-binding factors that bind to the core regulatory element of the HLA-A and HLB-B gene locus. A "novel" DNA-binding factor recognizing the CCAAT motif seems to be important for locus-specific expression of HLA-A mRNA, whereas a different factor which binds to a Sp1-like sequence is crucial for normal HLA-B mRNA expression. In certain colorectal cancer cell lines, underrepresentation of these locus-specific DNA-binding proteins correlates with the locus-specific down-regulation of HLA mRNA. This observation is further supported by experiments which demonstrated that the locus-specific suppression of exogenously introduced TK-chloramphenicol acetyltransferase DNA constructs, containing the "putative" HLA locus-specific DNA core regulatory sequence, is regulated in a locus-specific manner when introduced into these HLA-A- and HLA-B-deficient human colorectal cell lines.
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PMID:Locus-specific transcriptional control of HLA genes. 151 66

Products encoded by the class I Major Histocompatibility Complex (MHC) genes serve as restriction molecules which enable T cells to generate an immune response to specific antigens. Recently, many investigators have demonstrated the importance of class I antigens in enabling the host to regulate tumor growth in vivo. In this report, we have studied the regulation of HLA genes by hormones in human breast cancer cell lines. Eight lines were studied. Using HLA locus-specific DNA probes, the level of HLA-A and HLA-B specific mRNAs were found to be underrepresented in six of these cell lines when compared to an epithelial cell line derived from a normal lactating breast. Moreover, the expression of class I MHC mRNA in these cells correlated well with the level of chloramphenicol acetyltransferase (CAT) activity detected after the introduction of exogenous HLA-CAT DNA-constructs. It was also found that HLA expression in some of the breast carcinoma cell lines could be modulated by the addition of hormones. Hence, HLA mRNA expression in the cell line MCF-7 was enhanced by the addition of estrogen; but was down-regulated in the presence of dexamethasone. Conversely, for T-47D cells, HLA expression was suppressed by progesterone. These results indicate that hormones could have an influence on the expression of HLA genes and may therefore indirectly be involved in the regulation of tumor growth by the host's immune system.
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PMID:Modulation of MHC gene expression in human breast carcinoma cells by hormones. 263 11