Role of Selenium in Cancer, HIV Infection and Human Heal

硒被公认为是一种预防各种形式的癌症(如结肠癌、前列腺癌、肺癌和肝脏)、心脏病和抗病毒药物。这一因素也可能在延缓艾滋病毒阳性患者的衰老过程和延缓艾滋病的进展方面发挥作用。这种元素的有益效果至少部分归因于它作为氨基酸--硒半胱氨酸(SEC)存在于硒蛋白中。我们的计划集中在SEC被结合到蛋白质中的方式，特定的硒蛋白在人类健康中的作用，以及硒在HIV感染中的作用。由于Sec tRNA是硒蛋白生物合成的关键分子，我们建立了编码野生型和突变型Sec tRNA转基因小鼠，并建立了Sec tRNA标准基因敲除和条件基因敲除小鼠，以检测每个转基因小鼠对硒代谢的影响。我们先前观察到，野生型SEC tRNA的过度表达不影响硒蛋白的合成，但I6A突变型SEC tRNA的过度表达选择性地抑制SEC tRNA的成熟和特定硒蛋白的翻译。这项研究标志着转基因小鼠被基因工程改造为含有功能性tRNA转基因的第一个例子，将为研究特定硒蛋白在健康中的作用提供重要工具，并登上了著名杂志《分子和细胞生物学》的封面。我们现在已经产生了一种携带突变的SEC tRNA转基因基因的转基因小鼠，这种转基因基因具有T-&gt；反密码子摆动位置的碱基变化。这种tRNA在表达的tRNA基因产物的摆动位置产生I，并翻译UGU和UGC，以及SEC密码子UGA。我们目前正在分析这种tRNA对硒蛋白生物合成的影响。我们最近开始将我们的标准基因敲除小鼠与我们的转基因小鼠配对，以挽救依赖于野生型或突变型SEC tRNA转基因的硒蛋白的生物合成。此外，我们最近开始将我们的条件基因敲除小鼠与不同的Cre小鼠配对，以选择性地移除包括肝脏、前列腺、大脑和乳房在内的各种组织中的SEC tRNA基因(从而关闭硒蛋白的表达)。通过这种方式，我们可以评估硒蛋白在肝脏、前列腺、大脑和乳腺癌中的作用。在我们研究特定硒蛋白在人类健康中的作用的研究中，我们先前观察到15 kDa硒蛋白的几个特征(9月15日)与癌症病因之间的相关性。为了明确这种硒蛋白在细胞中的作用，我们正在准备一种靶向载体来敲除Sep 15基因，以产生缺乏该基因的小鼠。在我们涉及硒对人类健康影响的研究中，我们发现，与未感染细胞相比，培养中的HIV感染细胞缺乏硒蛋白，并且感染了猴免疫缺陷病毒(SIV)的恒河猴在发展为艾滋病的过程中出现缺硒，这在HIV阳性患者中是特有的。我们检查了培养中的SIV感染细胞，发现它们具有与HIV感染细胞非常相似的特征，包括硒蛋白缺乏以及通常与缺硒有关的SEC tRNA亚型的水平和分布减少。作为这些观察的结果，我们现在有了一个模型来理解与艾滋病相关的硒缺乏的分子机制。我们希望获得资金，在感染SIV的恒河猴身上进一步推行这一模型。

Selenium is recognized as a chemopreventive agent against various forms of cancer (e.g., colon, prostate, lung and liver), against heart disease, and as an antiviral agent. This element also likely plays a role in delaying the aging process and in delaying the progression of AIDS in HIV positive patients. The beneficial effects of this element are due, at least in part, to its presence in selenoproteins as the amino acid, selenocysteine (Sec). Our program focuses on the means by which Sec is incorporated into protein, the role of specific selenoproteins in human health and the role of selenium in HIV infection. As Sec tRNA is the key molecule in selenoprotein biosynthesis, we produced transgenic mice encoding wild type and mutant Sec tRNA transgenes and produced Sec tRNA standard knockout and conditional knockout mice to examine the effect of each genetically altered mouse on selenium metabolism. We observed previously that over-expression of wild type Sec tRNA does not affect selenoprotein synthesis, but that of an i6A mutant Sec tRNA, however, selectively inhibits Sec tRNA maturation and translation of specific selenoproteins. This study marked the first example of a transgenic mouse being genetically engineered to contain a functional tRNA transgene, will provide an important tool for studying the role of specific selenoproteins in health and was featured on the cover of the prestigious journal, Molecular and Cellular Biology. We have now generated a transgenic mouse line carrying mutant Sec tRNA transgenes that have a T -> A base change in the wobble position of the anticodon. This tRNA produces I in the wobble position of the expressed tRNA gene product and translates UGU and UGC in addition to the Sec codon, UGA. We are presently analyzing the effect of this tRNA on selenoprotein biosynthesis. We have recently begun to mate our standard knockout mice with our transgenic mice to rescue selenoprotein biosynthesis that is dependent on the wild type or mutant Sec tRNA transgene. In addition, we have recently begun to mate our conditional knockout mice with different Cre mice to selectively remove the Sec tRNA gene (and therefore shut off selenoprotein expression) in various tissues including liver, prostate, brain and breast. In this way, we can assess the role of selenoproteins in liver, prostate, brain and breast malignancy. In our studies on examining the role of specific selenoproteins in human health, we previously observed a correlation between several characteristics of the 15 kDa selenoprotein (Sep15) and cancer etiology. To specifically define the cellular role of this selenoprotein, we are preparing a targeting vector to knockout the Sep 15 gene for generating mice lacking this gene. In our studies involving the effects of selenium on human health, we have shown that HIV infected cells in culture have a deficient amount of selenoproteins compared to unifected cells and that Rhesus monkeys infected with simian immunodeficiency virus (SIV) develop selenium deficiency in the progression of developing AIDS as is characteristcally found in HIV positive patients. We examined SIV infected cells in culture and have found that they have very similar characteristics as HIV infected cells including selenoprotein deficiency and reduced levels and distributions of the Sec tRNA isoforms that are normally associated with selenium deficiency. As a result of these observations, we now have a model for understanding the molecular mechanism of selenium deficiency associated with AIDS. We hope to obtain funds to further pursue this model in Rhesus monkeys infected with SIV.