METABOLIC REGULATION OF APO B MRNA EDITING

肝脏合成和分泌载脂蛋白B（apo B）是 由饮食和激素因素调节代谢。 最近的证据 表明饮食和激素调节一种新的RNA加工形式， 称为mRNA编辑。 编辑的载脂蛋白B mRNA翻译成较低的 由于谷氨酰胺的转化而产生分子量蛋白质（apo B -L） 密码子到框内终止密码子通过特定的单碱基变化， 密码子2153处胞苷变为尿苷（CAA → UAA）。 大分子组装体 参与mRNA编辑（编辑体）最近已被确定， 体外，并建议进行特定的C->U转换， 载脂蛋白B cDNA亚克隆的核糖核酸探针。 RNA编辑和27 S编辑体 具有识别、组装和催化的特性 在许多其他依赖核糖核蛋白的过程中可见。 已经提出了免疫学、分子和生物化学技术 用于纯化编辑体，表征其大分子组成 并确定RNA识别和核苷酸识别的潜在机制 转换. 编辑体组分特异性单克隆抗体 将生产和免疫测定开发的定性和 结构和功能的定量分析。 这些研究报告将 辅之以使用突变体的编辑特异性的分子分析 apo B mRNA构建体，其集中于编辑位点侧翼的序列。 描述可能导致 在肝脏和肠道中观察到的编辑活性的定量差异 也将进行评估。 这项研究的重要性在于它的潜力， 描述了载脂蛋白B产生的代谢调节， mRNA编辑的机制和特定的大分子， 和/或交互参与控制。 的结果 拟议的研究对肝脏产生 LDL（未编辑的载脂蛋白B）和乳糜微粒的肠道产生（编辑） 载脂蛋白B）相对于这些可变的致动脉粥样硬化潜力 脂蛋白组分。此外，从 这些研究对于评价 mRNA编辑和识别可能作为编辑的其他mRNA 印刷受体.

Hepatic synthesis and secretion of apolipoprotein B (apo B) is metabolically regulated by dietary and hormonal factors. Recent evidence suggests that diet and hormones regulate a novel form of RNA processing known as mRNA editing. Edited apo B mRNA translates into a lower molecular weight protein (apo B -L) due to the conversion of a glutamine codon to an in-frame stop codon through a specific single base change of cytidine to uridine in codon 2153 (CAA->UAA). Macromolecular assemblies involved in mRNA editing (editosomes) have been recently identified in vitro and proposed to carry out the specific C->U conversion on riboprobes of apo B cDNA subclones. RNA editing and the 27S editosome have characteristic properties of recognition, assembly and catalysis seen with many other ribonucleoprotein-dependent processes. Immunological, molecular and biochemical techniques have been proposed for purifying editosomes, characterizing their macromolecular composition and determining the mechanism underlying RNA recognition and nucleotide conversion. Monoclonal antibodies specific for the editosome components will be produced and immunoassays developed for qualitative and quantitative analyses of structure and function. These studies will be complemented by molecular analysis of editing-specificity using mutant apo B mRNA constructs which focus on sequences flanking the editing site. Description of tissue-specific characteristics which might underlie the quantitative differences in editing activity seen in liver and intestine will also be evaluated. The significance of the proposed research lies in its potential to describe metabolic regulation of apo B production at the level of the mechanism of mRNA editing and the specific macromolecules whose synthesis and/or interactions participate in the control. The results of the proposed studies have implications regarding the hepatic production of LDL (unedited apo B) and intestinal production of chylomicrons (edited apo B) with respect to the variable atherogenic potential of these lipoprotein fractions in humans. Moreover, the information obtained in these studies will be important for evaluating the generic properties of mRNA editing and identifying other mRNAs which might serve as editing substrates.