Systems level understanding of selenoprotein biosynthesis

硒（Se）是一种微量元素，在脑功能、男性生殖和免疫功能等过程中发挥作用。在哺乳动物中，Se是必需元素，因为其以硒代半胱氨酸（Sec）残基的形式存在于蛋白质中。Sec被称为遗传密码中的第21个氨基酸，并且响应于UGA密码子协同插入蛋白质中，与蛋白质合成的终止竞争。几个硒蛋白基因的突变和单核苷酸多态性与疾病有关。我们以前开发的工具，可以有效地识别硒蛋白基因。使用这些工具，我们确定了人类和小鼠硒蛋白（硒蛋白组）。我们进一步开发的方法，支持硒，Sec和硒蛋白合成的综合分析，最显着的核糖体分析。我们准备通过解决该领域的关键问题，从这一基础中受益。首先，我们将描述Sec插入和终止蛋白质合成之间的竞争的影响。在UGA密码子处的Sec插入与终止竞争，这表明大量的截短蛋白质被合成，然后必须被细胞降解。器官间硒代谢的差异进一步加剧了这种情况。我们将利用核糖体分析来表征硒蛋白在小鼠不同器官中的合成，定义硒蛋白亚型，并表征截短硒蛋白的命运。其次，我们将确定在硒蛋白，组织和硒饮食的具体方式在不同器官的硒蛋白合成的速率和功能。使用核糖体分析在活体动物中，我们将确定在器官和个体硒蛋白水平的硒蛋白合成速率，表征硒蛋白合成的饮食硒调节，并检查在小鼠器官中转录丰度和硒蛋白合成水平的硒蛋白表达的平行调节。

Selenium (Se) is a trace element with roles in processes, such as brain function, male reproduction, and immune function. In mammals, Se is an essential element due to its presence in proteins in the form of selenocysteine (Sec) residue. Sec is known as the 21st amino acid in the genetic code and is co-translationally inserted into proteins in response to UGA codons, in competition with termination of protein synthesis. Mutations and single nucleotide polymorphisms in several selenoprotein genes have been associated with disease. We previously developed tools that allow efficient identification of selenoprotein genes. Using these tools, we identified sets of human and mouse selenoproteins (selenoproteomes). We further developed approaches that support integrative analyses of Se, Sec, and selenoprotein synthesis, most notably ribosome profiling. We are poised to benefit from this foundation by addressing critical questions in the field. First, we will characterize the impact of competition between Sec insertion and termination of protein synthesis. Sec insertion at UGA codons competes with termination, suggesting that large amounts of truncated proteins are synthesized and then must be degraded by the cells. This is further exacerbated by differences in Se metabolism among organs. We will utilize ribosome profiling to characterize selenoprotein synthesis in various organs of mice, define selenoprotein isoforms, and characterize the fate of truncated selenoproteins. Second, we will determine the rates and features of selenoprotein synthesis in various organs in a selenoprotein-, tissue-, and selenium diet-specific manner. Using ribosome profiling in live animals, we will determine the rates of selenoprotein synthesis at the level of organs and individual selenoproteins, characterize regulation of selenoprotein synthesis by dietary selenium, and examine parallel regulation of selenoprotein expression at the level of transcript abundance and selenoprotein synthesis in mouse organs.