REGULATION OF UREA CYCLE ENZYME SYNTHESIS

尿素循环酶合成的调控

• 批准号: 3231502
• 负责人: SIDNEY MACHEN MORRIS
• 金额: $ 7.67万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 1983
• 资助国家: 美国
• 起止时间: 1983-12-01 至 1986-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3231502
• 关键词: affinity chromatography; carbamoylphosphate synthase; complementary DNA; genetic library; genetic manipulation; genetic transcription; hormone regulation /control mechanism; larva; liver metabolism; messenger RNA; thyroxine; tissue /cell culture; urea cycle

Thyroid hormone produces a coordinate increase in the levels of all five enzymes of the urea cycle in liver of the bullfrog tadpole (Rana catesbeiana). Preliminary experiments demonstrate that for at least two of the urea cycle enzymes in tadpole liver -- argininosuccinate synthetase and carbamyl phosphate synthetase I -- the increase in enzyme levels reflects a several-fold increase in the corresponding mRNA levels. The proposed research is directed toward elucidating the molecular mechanisms whereby thyroid hormone regulates the levels of the mRNAs for the urea cycle enzymes. I plan to construct a cDNA library for bullfrog liver and isolate cDNA clones for argininosuccinate synthetase and carbamyl phosphate synthetase I. Using RNA-DNA hybridization assays, I plan to analyze in detail the response of the mRNA levels for these enzymes to thyroid hormone. A major objective of the research is to determine whether regulation of the specific mRNA levels occurs primarily at the transcriptional or post-transcriptional level. Experiments using primary cultures of tadpole hepatocytes will determine whether thyroid hormone alone or in combination with other hormones acts directly to elicit the increases in mRNA levels for the urea cycle enzymes observed in the intact animal. Although the relative synthesis rates and/or mRNA levels for a number of proteins have been shown to change following administration of thyroid hormone to intact animals, a direct effect of thyroid hormone alone on specific mRNA levels in isolated cells in culture has to date been demonstrated for only two identified proteins: avian malic enzyme and rat growth hormone. Neither of these has been shown to be coordinatley regulated with other proteins of known function by thyroid hormone alone. The tadpole liver is potentially useful in providing an experimental system for studying the molecular mechanisms of thyroid hormone action in early development, especially for coordinate regulation of the different enzymes of an important metabolic pathway.

甲状腺激素均产生所有五个水平的坐标增加 牛蛙tadpole的肝周期的酶（rana Catesbeiana）。 初步实验表明，至少有两个 the tadpole肝脏中的尿素周期酶 - 精氨酸核酸合成酶 和磷酸氨基甲酰磷酸合成酶I-酶水平的增加 反映了相应的mRNA水平增加了几倍。 这 提出的研究针对阐明分子机制 甲状腺激素调节尿素的mRNA水平 循环酶。 我计划为牛肉肝构建cDNA库， 分离的cDNA克隆，用于精氨酸糖酸合成酶和磷酸氨基甲酰磷酸酯 合成酶I.使用RNA-DNA杂交分析，我计划在 详细说明这些酶对甲状腺的mRNA水平的响应 激素。 该研究的主要目的是确定是否 特定mRNA水平的调节主要发生在 转录或转录后水平。 使用主要的实验 t刺肝细胞的培养物将确定甲状腺激素是否是否 单独或与其他激素联合起来直接引起 在完整中观察到的尿素周期酶的mRNA水平增加 动物。 尽管A的相对合成率和/或mRNA水平 蛋白质的数量已显示在给药后改变 甲状腺激素对完整动物，仅甲状腺激素的直接作用 迄今为止，在培养细胞中的特定mRNA水平上一直存在 仅适用于两种已鉴定的蛋白质：禽麦芽酶和大鼠 生长激素。 这些都没有被证明是coordinatley 单独用甲状腺激素的其他已知功能的蛋白质调节。 t肝脏在提供实验系统方面可能有用 用于研究早期甲状腺激素作用的分子机制 开发，特别是用于协调不同酶的调节 重要的代谢途径。