Yeow W S, Au W C, Juang Y T, Fields C D, Dent C L, Gewert D R, Pitha P M
Oncology Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
J Biol Chem. 2000 Mar 3;275(9):6313-20. doi: 10.1074/jbc.275.9.6313.
Type I interferons constitute an important part of the innate immune response against viral infection. Unlike the expression of interferon (IFN) B gene, the expression of IFNA genes is restricted to the lymphoid cells. Both IFN regulatory factor 3 and 7 (IRF-3 and IRF-7) were suggested to play positive roles in these genes expression. However, their role in the differential expression of individual subtypes of human IFNA genes is unknown. Using various IFNA reporter constructs in transient transfection assay we found that overexpression of IRF-3 in virus infected 2FTGH cells selectively activated IFNA1 VRE, whereas IRF-7 was able to activate IFNA1, A2, and A4. The binding of recombinant IRF-7 and IRF-3 to these VREs correlated with their transcriptional activation. Nuclear proteins from infected and uninfected IRF-7 expressing 2FTGH cells formed multiple DNA-protein complexes with IFNA1 VRE, in which two unique DNA-protein complexes containing IRF-7 were detected. In 2FTGH cells, virus stimulated expression of IFNB gene but none of the IFNA genes. Reconstitution of IRF-7 synthesis in these cells resulted, upon virus infection, in the activation of seven endogenous IFNA genes in which IFNA1 predominated. These studies suggest that IRF-7 is a critical determinant for the induction of IFNA genes in infected cells.
I型干扰素是针对病毒感染的固有免疫反应的重要组成部分。与干扰素（IFN）β基因的表达不同，IFNA基因的表达仅限于淋巴细胞。干扰素调节因子3和7（IRF-3和IRF-7）均被认为在这些基因的表达中发挥积极作用。然而，它们在人类IFNA基因各个亚型差异表达中的作用尚不清楚。通过在瞬时转染实验中使用各种IFNA报告基因构建体，我们发现，在病毒感染的2FTGH细胞中过表达IRF-3可选择性激活IFNA1病毒反应元件（VRE），而IRF-7能够激活IFNA1、A2和A4。重组IRF-7和IRF-3与这些VRE的结合与其转录激活相关。来自感染和未感染的表达IRF-7的2FTGH细胞的核蛋白与IFNA1 VRE形成多个DNA-蛋白质复合物，其中检测到两个含有IRF-7的独特DNA-蛋白质复合物。在2FTGH细胞中，病毒刺激IFNβ基因的表达，但不刺激任何IFNA基因的表达。在这些细胞中重建IRF-7合成后，病毒感染会导致7个内源性IFNA基因被激活，其中IFNA1占主导。这些研究表明，IRF-7是感染细胞中诱导IFNA基因的关键决定因素。
