Kaminuma Osamu, Kitamura Fujiko, Kitamura Noriko, Hiroi Takachika, Miyoshi Hiroyuki, Miyawaki Atsushi, Miyatake Shoichiro
Cytokine Project, Department of Allergy and Immunology, The Tokyo Metropolitan Institute of Medical Science, Japan.
J Immunol. 2008 Jan 1;180(1):319-26. doi: 10.4049/jimmunol.180.1.319.
The NFAT family transcription factors play crucial roles in immunological and other biological events; however, the functional differences among NFAT members have not been fully elucidated. This study investigated the relative contribution of NFATc2 and NFATc1 to the transactivation of cytokine genes in T cells. Ectopic expression of NFATc2 but not NFATc1, especially its short isoform, enhanced TNF-alpha synthesis in human T cells at the gene transcription level, whereas both NFATs augmented IL-2 expression. In addition, a reduction of the shortest NFATc1 isoform using RNA interference technology failed to suppress TNF-alpha expression. The promoter/enhancer activity of the NFAT-binding site in the TNF-alpha gene was up-regulated by NFATc2 but not by NFATc1, whereas both NFATs associated similarly with this region. A study of mRNA expression using NFATc2/NFATc1 chimeric molecules revealed that the enhancing activity of NFAT on the TNF-alpha gene was lost by truncation of its C-terminal transactivation domain. In addition, this domain derived from NFATc2 behaved as a dominant negative against the NFAT site in TNF-alpha promoter-dependent transcriptional activity in T cells. We conclude that the C-terminal transactivation domain in NFAT is crucial for TNF-alpha gene expression in human T cells.
NFAT家族转录因子在免疫及其他生物学事件中发挥着关键作用；然而，NFAT成员之间的功能差异尚未完全阐明。本研究调查了NFATc2和NFATc1对T细胞中细胞因子基因反式激活的相对贡献。NFATc2而非NFATc1（尤其是其短异构体）的异位表达，在基因转录水平增强了人T细胞中TNF-α的合成，而两种NFAT均增强了IL-2的表达。此外，使用RNA干扰技术减少最短的NFATc1异构体未能抑制TNF-α的表达。TNF-α基因中NFAT结合位点的启动子/增强子活性被NFATc2上调，但未被NFATc1上调，而两种NFAT与该区域的结合相似。使用NFATc2/NFATc1嵌合分子对mRNA表达的研究表明，NFAT对TNF-α基因的增强活性因截短其C末端反式激活结构域而丧失。此外，源自NFATc2的该结构域在T细胞中对TNF-α启动子依赖性转录活性中的NFAT位点表现为显性阴性。我们得出结论，NFAT中的C末端反式激活结构域对人T细胞中TNF-α基因表达至关重要。
