Ogilvie Rachel L, Sternjohn Julius R, Rattenbacher Bernd, Vlasova Irina A, Williams Darlisha A, Hau Heidi H, Blackshear Perry J, Bohjanen Paul R
Centers for Infectious Diseases and Microbiology Translational Research and Immunology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Biol Chem. 2009 Apr 24;284(17):11216-23. doi: 10.1074/jbc.M901229200. Epub 2009 Mar 3.
Tristetraprolin (TTP) regulates expression at the level of mRNA decay of several cytokines, including the T cell-specific cytokine, interleukin-2. We performed experiments to determine whether another T cell-specific cytokine, interferon-gamma (IFN-gamma), is also regulated by TTP and found that T cell receptor-activated T cells from TTP knock-out mice overproduced IFN-gamma mRNA and protein compared with activated T cells from wild-type mice. The half-life of IFN-gamma mRNA was 23 min in anti-CD3-stimulated T cells from wild-type mice, whereas it was 51 min in anti-CD3-stimulated T cells from TTP knock-out mice, suggesting that the overexpression of IFN-gamma mRNA in TTP knock-out mice was due to stabilization of IFN-gamma mRNA. Insertion of a 70-nucleotide AU-rich sequence from the murine IFN-gamma 3'-untranslated region, which contained a high affinity binding site for TTP, into the 3'-untranslated region of a beta-globin reporter transcript conferred TTP-dependent destabilization on the beta-globin transcript. Together these results suggest that TTP binds to a functional AU-rich element in the 3'-untranslated region of IFN-gamma mRNA and mediates rapid degradation of the IFN-gamma transcript. Thus, TTP plays an important role in turning off IFN-gamma expression at the appropriate time during an immune response.
锌指蛋白36（TTP）在包括T细胞特异性细胞因子白细胞介素-2在内的多种细胞因子的mRNA降解水平上调节其表达。我们进行了实验以确定另一种T细胞特异性细胞因子γ干扰素（IFN-γ）是否也受TTP调节，结果发现与野生型小鼠的活化T细胞相比，来自TTP基因敲除小鼠的T细胞受体激活的T细胞过量产生IFN-γ mRNA和蛋白。在野生型小鼠的抗CD3刺激的T细胞中，IFN-γ mRNA的半衰期为23分钟，而在TTP基因敲除小鼠的抗CD3刺激的T细胞中，其半衰期为51分钟，这表明TTP基因敲除小鼠中IFN-γ mRNA的过表达是由于IFN-γ mRNA的稳定性增加所致。将来自小鼠IFN-γ 3'非翻译区的一段70个核苷酸的富含AU序列（其中包含一个与TTP的高亲和力结合位点）插入β-珠蛋白报告转录本的3'非翻译区，赋予了β-珠蛋白转录本TTP依赖性的去稳定化作用。这些结果共同表明，TTP与IFN-γ mRNA 3'非翻译区中的一个功能性富含AU元件结合，并介导IFN-γ转录本的快速降解。因此，TTP在免疫反应的适当时间关闭IFN-γ表达中发挥重要作用。
