ROLE OF SELENIUM IN PREVENTING CANCER, HEART DISEASE AND DELAYING AGING PROCESS

硒是哺乳动物饮食中的一种必需元素，含量太少。 或者在狭窄的范围内摄入过多的食物可能会产生毁灭性的影响 对健康的影响。硒具有预防心脏病和预防心脏病的作用 与预防癌症和延缓衰老有关 进程。该元素部分地通过其 硒蛋白中的一种氨基酸，即硒半胱氨酸。我们, 因此，他们将重点放在硒半胱氨酸被 在tRNA上生物合成，并结合到蛋白质中。在过去 一年来，我们发现果蝇含有两种硒半胱氨酸 同种受体，其水平在发育过程中不变。 这些同种受体的基因映射到染色体上的一个单一基因座上。 2在47E或F区域，我们进一步发现，硒半胱氨酸 TRNA群体至少包含两个额外的同位受体，它们是 在缺硒大鼠的肌肉组织中大量富含。 该元素对缺硒大鼠的再补充显示 硒半胱氨酸tRNA群体的增强和在 硒半胱氨酸异构体的分布。这一速度 然而，变化在不同组织中是不同的(例如，分布 肝脏中的等量受体恢复到富硒大鼠的水平 24-48小时，而肌肉中的蛋白质在72小时仍不完全)。 硒半胱氨酸一级结构的大部分分子结构变化 对硒作出反应的tRNA正在非洲爪哇进行检测 TRNA中修饰碱基的合成动力学有 已被详细确定。硒半胱氨酸tRNA在大肠杆菌中的转录 添加突变株的HeLa细胞和非洲爪哇卵母细胞提取液 TATA盒结合蛋白显示了TATA盒的共同表面 结合蛋白用于转录该基因和POL II 转录的基因，即使这种tRNA在POL III中表达。

Selenium is an essential element in the diet of mammals and too little or too much in the diet within a narrow range can have devastating effects on health. Selenium has a role in preventing heart disease and has been implicated in preventing cancer and in delaying the aging process. This element exerts its effects, in part, through its presence in selenoproteins as the amino acid, selenocysteine. We, therefore, are focusing on the means by which selenocysteine is biosynthesized on tRNA and is incorporated into protein. In the past year, we have found that Drosophila contain two selenocysteine isoacceptors, the levels of which are not changed during development. The gene for these isoacceptors maps to a single locus on chromosome 2 at regions 47 E or F. Further, we have found that the selenocysteine tRNA population contains at least two additional isoacceptors which are vastly enriched in muscle tissues of selenium deficient rats. Resupplementation of selenium deficient rats with this element shows an enhancement in the selenocysteine tRNA population and alteration in the distribution of the selenocysteine isoacceptors. The rate of change varies, however, in different tissues (e.g., the distribution of isoaccep-tors in liver returns to that in selenium adequate rats at 24-48 hours while that in muscle was still incom-plete at 72 hours). Most of the molecular changes in primary structure of selenocysteine tRNAs that occur in response to selenium are being examined in Xenopus oocytes where the kinetics of synthesis of modified bases in tRNA have been determined in detail. Transcription of selenocysteine tRNA in HeLa cell and Xenopus oocyte extracts that are supplemented with mutant TATA box binding proteins show that common surfaces of the TATA box binding protein are used for transcribing this gene and Pol II transcribed genes even though this tRNA is expressed by Pol III.