人A33基因5′调控区的组织特异性表达元件

在对人A33基因 5′调控区初步研究的基础上 ,进一步采用体外足迹法、电泳迁移率变更分析(EMSA)和定点突变等实验对A33启动子的 - 10 4～ + 2 5bp区域进行了重点研究 .在A33启动子的- 10 4～ + 2 5bp区域内存在两个转录正调控元件 ,它们分别位于转录起始位点上游 - 86～ - 6 8区(A)和 - 40～ - 19区 (B) .通过对转录因子数据库的查找 ,发现A区与转录因子GKLF (gut enrichedKr櫣ｐｐｅｌ likefactor)的结合位点吻合 ,而B区则没有找到与之相应的转录因子 .EMSA实验表明 ,A区与核蛋白的结合存在组织特异性 ,而B区的结合则无组织特异性 .推测A区所包含的顺式调控元件很可能是决定A33基因组织特异性表达的关键元件 .根据B区所处的位置和富含AT来分析 ,它极有可能是和通用转录因子及RNA聚合酶结合的区域 .A和B两个区域的点突变都可使A33启动子的活性丧失 85 %以上     

Three distinct RNA sequence elements are required for efficient apolipoprotein B (apoB) RNA editing in vitro.

Apolipoprotein B (apoB) mRNA is edited in rat liver and intestine to convert a CAA glutamine codon to a UAA translational stop codon by the direct conversion of cytidine to uridine at nucleotide 6666. We have proposed the 'mooring sequence' model for apoB RNA editing, in which editing complexes (editosomes) assemble on specific apoB mRNA flanking sequences to direct this site-specific editing event. One sequence element (approx. nts 6671-81, the presumed 'mooring sequence') has been previously identified as necessary for editing. We have identified two additional sequence elements which are necessary for efficient editing: (1) a 5' 'Regulator' region which modulates editing efficiency and (2) a 'Spacer' region between the editing site and the 3' mooring sequence, whose distance is critical for efficient editing. Utilizing this data, we have induced editing at a cryptic site and have defined a 22 nucleotide 'cassette' of specific apoB sequence which is sufficient to support wild-type levels of editing in vitro in a background of distal apoB RNA sequence.     

Inhibition of both the apical sodium-dependent bile acid transporter and HMG-CoA reductase markedly enhances the clearance of LDL apoB

Discovery of the ileal apical sodium-dependent bile acid transporter (ASBT) permitted development of specific inhibitors of bile acid reabsorption, potentially a new class of cholesterol-lowering agents. In the present study, we tested the hypothesis that combining the novel ASBT inhibitor, SC-435, with the HMG-CoA reductase inhibitor, atorvastatin, would potentiate reductions in LDL cholesterol (LDL-C) and LDL apolipoprotein B (apoB). ApoB kinetic studies were performed in miniature pigs fed a typical human diet and treated with the combination of SC-435 (5 mg/kg/day) plus atorvastatin (3 mg/kg/day) (SC-435+A) or a placebo. SC-435+A decreased plasma total cholesterol by 23% and LDL-C by 40%. Multicompartmental analysis (SAAM II) demonstrated that LDL apoB significantly decreased by 35% due primarily to a 45% increase in the LDL apoB fractional catabolic rate (FCR). SC-435+A significantly decreased hepatic concentrations of free cholesterol and cholesteryl ester, and increased hepatic LDL receptor mRNA consequent to increased cholesterol 7alpha-hydroxylase expression and activity. In comparison, SC-435 (10 mg/kg/day) monotherapy decreased LDL apoB by 10% due entirely to an 18% increase in LDL apoB FCR, whereas atorvastatin monotherapy (3 mg/kg/day) decreased LDL apoB by 30% due primarily to a 22% reduction in LDL apoB production. We conclude that SC-435+A potentiates the reduction of LDL-C and LDL apoB due to complementary mechanisms of action.