Homma Takujiro, Ishibashi Daisuke, Nakagaki Takehiro, Fuse Takayuki, Sano Kazunori, Satoh Katsuya, Atarashi Ryuichiro, Nishida Noriyuki
1] Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan [2].
Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Sci Rep. 2014 Aug 8;4:6006. doi: 10.1038/srep06006.
As a prompt response against invasion of various viruses, interferon regulatory factor-3 (IRF-3) is initially phosphorylated to become activated and upregulates mainly Type I Interferons (IFN-I) in most cell types. We previously reported that IRF-3-dependent host innate immune responses partially interfere in infection of prions. Here, we found that stable infection of prion suppressed IRF-3 gene-expression. The decreased promoter activity of IRF-3 was significantly restored along with treatment of anti-prion drugs in the prion-infected cells, suggesting that infection of prion directly influence the regulation of IRF-3 transcription. We further investigated promoter activity of 5'- flanking region of murine IRF-3 using a luciferase reporter system and found that the nucleotides -119 to -1 were indispensable for the promoter activity. Within this region, mutations in the Oct-1 binding site significantly reduced the promoter activity and chromatin immunoprecipitation (ChIP) assay revealed that Oct-1 indeed binds to the region. In addition, overexpression of Oct-1 increased the promoter activity of IRF-3. Intriguingly, Oct-1 protein was significantly reduced in prion-infected cells and mice brains compared with uninfected groups. Taken together, we concluded that prion infection could interfere in the function of Oct-1, resulting in the down-regulation of IRF-3.
作为对各种病毒入侵的快速反应，干扰素调节因子3（IRF-3）最初会发生磷酸化而被激活，并在大多数细胞类型中主要上调I型干扰素（IFN-I）。我们之前报道过，依赖IRF-3的宿主固有免疫反应会部分干扰朊病毒的感染。在此，我们发现朊病毒的稳定感染会抑制IRF-3基因的表达。在朊病毒感染的细胞中，随着抗朊病毒药物的处理，IRF-3降低的启动子活性得到了显著恢复，这表明朊病毒感染直接影响IRF-3转录的调控。我们进一步使用荧光素酶报告系统研究了小鼠IRF-3 5'-侧翼区域的启动子活性，发现核苷酸-119至-1对于启动子活性是不可或缺的。在该区域内，Oct-1结合位点的突变显著降低了启动子活性，染色质免疫沉淀（ChIP）分析表明Oct-1确实与该区域结合。此外，Oct-1的过表达增加了IRF-3的启动子活性。有趣的是，与未感染组相比，朊病毒感染的细胞和小鼠大脑中Oct-1蛋白显著减少。综上所述，我们得出结论，朊病毒感染可能会干扰Oct-1的功能，从而导致IRF-3的下调。
