Chuang S S, Das H K
Department of Pharmacology, University of North Texas, The Health Science Center at Fort Worth, 76107, USA.
Biochem Biophys Res Commun. 1996 Mar 27;220(3):553-62. doi: 10.1006/bbrc.1996.0442.
Apolipoprotein B is the sole protein of low density lipoprotein and is produced primarily in the liver. Previously, we have identified two cis-acting elements (+20 to +40; +43 to +53) in the non-translated exon of the human apolipoprotein B gene, using DNase I footprint analysis (S. S. Chuang, H. Zhuang, S. R. Reisher, S. I. Feinstein, and H. K. Das, Biochem. Biophys. Res. Com. 215, 394-404, 1995). Wild type and mutated promoter constructs were used as templates in DNase I footprint analysis with rat liver nuclear extracts. These experiments suggest that trans-acting factors BRF-3 and BRF-4 which recognize these two footprint regions (+20 to +40; +43 to +53) respectively, act independently. In vitro-synthesized hepatocyte nuclear factors HNF-1alpha, HNF-lbeta. HNF-3alpha, and HNF-2/HNF-4 showed no specific protein/DNA interaction with these regions. DNase I footprint analysis using other DNA-binding site oligonucleotides as competitors indicated that BRF-3 and BRF-4 could be different hepatocyte nuclear factors and may contribute to the regulation of transcription of the human apolipoprotein B gene.
载脂蛋白B是低密度脂蛋白的唯一蛋白质，主要在肝脏中产生。此前，我们使用DNA酶I足迹分析（S.S.庄、H.庄、S.R.赖舍尔、S.I.费恩斯坦和H.K.达斯，《生物化学与生物物理学研究通讯》215，394 - 404，1995）在人载脂蛋白B基因的非翻译外显子中鉴定出两个顺式作用元件（+20至+40；+43至+53）。野生型和突变型启动子构建体在与大鼠肝核提取物进行的DNA酶I足迹分析中用作模板。这些实验表明，分别识别这两个足迹区域（+20至+40；+43至+53）的反式作用因子BRF - 3和BRF - 4独立发挥作用。体外合成的肝细胞核因子HNF - 1α、HNF - 1β、HNF - 3α和HNF - 2/HNF - 4与这些区域没有特异性的蛋白质/DNA相互作用。使用其他DNA结合位点寡核苷酸作为竞争者进行的DNA酶I足迹分析表明，BRF - 3和BRF - 4可能是不同的肝细胞核因子，可能有助于调节人载脂蛋白B基因的转录。
