Human Acyl-coenzyme A: Cholesterol Acyltransferase Enzyme-1 Gene Expression And Regulation

Human Acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) cDNA Kl is distributed over two different chromosomes (chromosome 1 and 7) with two separate promoters, designated as PI and P7. This work was mainly focused on the transcriptional regulation of human ACAT-1 gene P7 promoter activity, and the effect of fatty acids on human ACAT1 gene expression.To test the P7 promoter activity, a series of constructs were obtained by cloning the different DNA fragments into the luciferase gene reporter vector pGL3-B. When the constructs were transiently transfected into THP-1 cells, luciferase activity assay showed that the core region of P7 promoter located at --165 bp. Tumor necrosis factor (TNF), a cytkine that exerts many pro-atherosclerotic effects in vivo, causes up-regulation of ACAT-1 gene expression in human blood monocytes. By luciferase activity assay, TNF-a enhanced ACAT-1 P7 promoter activity in THP-1 monocytic cell line.Fatty acid is a substrate of ACAT-1 and influences cholesterol homeostasis related with atherosclerosis. It is reported that high fatty acid diet may enhance ACAT-1 expression. The preliminary results by analysis of luciferase activity assays and Western blot showed that palmitic acid (C16) and oleic acid (C18:lco 9) might have different effect on human ACAT-1 PI promoter activity and ACAT-1 expression in HepG2 was possibly down-regulated by palmitic acid (C16), stearic acid (CIS) and arachidic acid (C20).