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K Reue

Publications and source records attributed to K Reue.

40 records · Page 3Linked to original sources
PubMed1989

A regulatory element in the ApoCIII promoter that directs hepatic specific transcription binds to proteins in expressing and nonexpressing cell types.

To better understand the mechanisms that determine cell type-specific gene expression, we have examined the transcriptional activity of a 13-nucleotide long sequence element, designated C3P, located in the promoter of the apoCIII gene. We demonstrate that this element is required for high levels of apoCIII gene expression in hepatic cells and is sufficient to determine hepatic specific expression when introduced into a heterologous promoter. A protein was identified in hepatic cell nuclear extracts, designated AF-1, that binds to this sequence and is presumably responsible for its transcriptional activity in hepatic cells. Even though the C3P element is not active in HeLa cells, a protein with C3P binding specificity was identified in HeLa cell nuclear extracts. While the HeLa protein is similar to the hepatic AF-1 in its binding specificity and relative abundance, it has approximately twice the molecular weight of the hepatic protein, indicating that they are different proteins or different forms of the same protein. A variety of murine tissue types, including those that do not express the apoCIII gene, were found to contain C3P binding proteins. We conclude that the cell type-specific activity of the C3P element is not due to the absence of C3P binding proteins in nonexpressing cells but is the result of qualitative differences in C3P binding proteins in different cell types.

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PubMed1988

Human apolipoprotein CIII gene expression is regulated by positive and negative cis-acting elements and tissue-specific protein factors.

Apolipoprotein CIII (apoCIII) is a major protein constituent of triglyceride-rich lipoproteins and is synthesized primarily in the liver. Cis-acting DNA elements required for liver-specific apoCIII gene transcription were identified with transient expression assays in the human hepatoma (HepG2) and epithelial carcinoma (HeLa) cell lines. In liver cells, 821 nucleotides of the human apoCIII gene 5'-flanking sequence were required for maximum levels of gene expression, while the proximal 110 nucleotides alone were sufficient. No expression was observed in similar studies with HeLa cells. The level of expression was modulated by a combination of positive and negative cis-acting sequences, which interact with distinct sets of proteins from liver and HeLa cell nuclear extracts. The proximal positive regulatory region shares homology with similarly located sequences of other genes strongly expressed in the liver, including alpha 1-antitrypsin and other apolipoprotein genes. The negative regulatory region is strikingly homologous to the human beta-interferon gene regulatory element. The distal positive region shares homology with some viral enhancers and has properties of a tissue-specific enhancer. The regulation of the apoCIII gene is complex but shares features with other genes, suggesting shuffling of regulatory elements as a common mechanism for cell type-specific gene expression.

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PubMed1987

Ath-1, a gene determining atherosclerosis susceptibility and high density lipoprotein levels in mice.

High density lipoprotein (HDL) is the major plasma lipoprotein found in mice fed normal laboratory chow containing 4% fat. When female mice from some inbred strains, such as C57BL/6, are fed a high fat diet (1.25% cholesterol, 15% fat, and 0.5% cholic acid), the levels of HDL-cholesterol decrease by about 50%, and lipid staining lesions form in the aorta within 14 weeks. In other strains of mice, such as C3H and BALB/c, HDL-lipid levels decrease only slightly, and few or no aortic lesions are observed at 14 weeks. The genetic basis of these phenotypic differences was analyzed by using recombinant inbred strains derived from C57BL/6 and BALB/c and also from C57BL/6 and C3H/He. The two phenotypes segregated as simple Mendelian traits, and no recombination was observed between them. Thus, HDL-cholesterol levels and susceptibility to atherosclerosis appear to be determined by the same gene (or by two closely linked genetic factors that are a maximum of 1.7 centimorgans apart). This gene was named Ath-1, for atherosclerosis susceptibility, with alleles r for resistance and s for susceptibility. Ath-1 maps on chromosome 1 near Alp-2, a gene that determines the structure of apolipoprotein A-II, one of the two major proteins found in HDL. Ath-1 is clearly separable from Alp-2, and the distance between these genes is 6.0 centimorgans with a standard error of 4.2 centimorgans. In humans, levels of HDL are inherited and are inversely correlated with atherosclerosis; familial hyperalphalipoproteinemia is associated with high levels of HDL-cholesterol and decreased risk of heart disease. The human trait phenotypically resembles Ath-1 in the mouse.

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