Kumaraswamy Easwari, Carlson Bradley A, Morgan Fanta, Miyoshi Keiko, Robinson Gertraud W, Su Dan, Wang Shulin, Southon Eileen, Tessarollo Lino, Lee Byeong Jae, Gladyshev Vadim N, Hennighausen Lothar, Hatfield Dolph L
Section on Molecular Biology of Selenium, Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Mol Cell Biol. 2003 Mar;23(5):1477-88. doi: 10.1128/MCB.23.5.1477-1488.2003.
Mice homozygous for an allele encoding the selenocysteine (Sec) tRNA [Ser]Sec gene (Trsp) flanked by loxP sites were generated. Cre recombinase-dependent removal of Trsp in these mice was lethal to embryos. To investigate the role of Trsp in mouse mammary epithelium, we deleted this gene by using transgenic mice carrying the Cre recombinase gene under control of the mouse mammary tumor virus (MMTV) long terminal repeat or the whey acidic protein promoter. While both promoters target Cre gene expression to mammary epithelium, MMTV-Cre is also expressed in spleen and skin. Sec tRNA [Ser]Sec amounts were reduced by more than 70% in mammary tissue with either transgene, while in skin and spleen, levels were reduced only with MMTV-Cre. The selenoprotein population was selectively affected with MMTV-Cre in breast and skin but not in the control tissue, kidney. Moreover, within affected tissues, expression of specific selenoproteins was regulated differently and often in a contrasting manner, with levels of Sep15 and the glutathione peroxidases GPx1 and GPx4 being substantially reduced. Expression of the tumor suppressor genes BRCA1 and p53 was also altered in a contrasting manner in MMTV-Cre mice, suggesting greater susceptibility to cancer and/or increased cell apoptosis. Thus, the conditional Trsp knockout mouse allows tissue-specific manipulation of Sec tRNA and selenoprotein expression, suggesting that this approach will provide a useful tool for studying the role of selenoproteins in health.
构建了硒代半胱氨酸（Sec）tRNA[Ser]Sec基因（Trsp）两侧带有loxP位点的等位基因纯合小鼠。在这些小鼠中，Cre重组酶依赖性地去除Trsp对胚胎是致死的。为了研究Trsp在小鼠乳腺上皮中的作用，我们通过使用在小鼠乳腺肿瘤病毒（MMTV）长末端重复序列或乳清酸性蛋白启动子控制下携带Cre重组酶基因的转基因小鼠来删除该基因。虽然这两个启动子都将Cre基因表达靶向乳腺上皮，但MMTV-Cre在脾脏和皮肤中也有表达。使用任一转基因时，乳腺组织中的Sec tRNA[Ser]Sec含量降低了70%以上，而在皮肤和脾脏中，只有使用MMTV-Cre时水平才会降低。硒蛋白群体在乳腺和皮肤中受到MMTV-Cre的选择性影响，但在对照组织肾脏中则没有。此外，在受影响的组织中，特定硒蛋白的表达受到不同的调节，且往往呈相反的方式，Sep15以及谷胱甘肽过氧化物酶GPx1和GPx4的水平大幅降低。在MMTV-Cre小鼠中，肿瘤抑制基因BRCA1和p53的表达也以相反的方式发生改变，表明对癌症的易感性更高和/或细胞凋亡增加。因此，条件性Trsp基因敲除小鼠允许对Sec tRNA和硒蛋白表达进行组织特异性操作，表明这种方法将为研究硒蛋白在健康中的作用提供一个有用的工具。
