Zhou Jie, Huang Jian-Dong, Poon Vincent K M, Chen Ding-Qiang, Chan Chris C S, Ng Fai, Guan Xin-Yuan, Watt Rory M, Lu Liwei, Yuen Kwok-Yung, Zheng Bo-Jian
Department of Microbiology, Research Centre of Infection and Immunology, The University of Hong Kong, Pokfulam, Hong Kong.
J Hepatol. 2009 Aug;51(2):322-32. doi: 10.1016/j.jhep.2009.03.020. Epub 2009 May 3.
BACKGROUND/AIMS: We previously demonstrated that two linked single nucleotide polymorphisms (SNPs) at -408 and -3 of type I interferon receptor 1 (IFNAR1) promoter are associated with susceptibility to chronic HBV infection. We aimed to elucidate the mechanism by which -3 and/or -408 C/T SNPs had such profound effects.
A functional SNP in IFNAR1 promoter was defined by reporter gene assay, mutational analysis, flow cytometry analysis and gel shift assay. The nuclear protein binding to the essential polymorphic site was identified and its effect on transcriptional regulation of IFNAR1 was further demonstrated in a series of ex vivo and in vivo experiments.
We found C>T change at the -3 locus reduced the transcriptional activity of IFNAR1 promoter. High mobility group B protein 1 (HMGB1) and PARP-1 were co-recruited to the IFNAR1 promoter to regulate its transcription. We demonstrated HMGB1-binding affinity to IFNAR1 promoter was reduced in the -3T variant. Additionally, PARP-1, a cofactor for IFNAR1 transcription activation, was significantly suppressed by HBV.
Upon HBV infection, decreased binding affinity of HMGB1 to the IFNAR1 promoter -3T variant is aggravated by the suppressed PARP-1 expression caused by HBV, resulting in a further attenuated IFNAR1 expression. This compromises the antiviral and immuno-regulatory effects of IFN-alpha/beta, which may in turn affect the clinical outcome of HBV infection.
背景/目的：我们之前证明，I型干扰素受体1（IFNAR1）启动子-408和-3位点的两个连锁单核苷酸多态性（SNP）与慢性HBV感染的易感性相关。我们旨在阐明-3和/或-408 C/T SNP产生如此深远影响的机制。
通过报告基因检测、突变分析、流式细胞术分析和凝胶迁移试验确定IFNAR1启动子中的功能性SNP。鉴定与必需多态性位点结合的核蛋白，并在一系列体外和体内实验中进一步证明其对IFNAR1转录调控的作用。
我们发现-3位点的C>T变化降低了IFNAR1启动子的转录活性。高迁移率族B蛋白1（HMGB1）和聚（ADP-核糖）聚合酶-1（PARP-1）共同被招募到IFNAR1启动子以调节其转录。我们证明-3T变异体中HMGB1与IFNAR1启动子的结合亲和力降低。此外，PARP-1作为IFNAR1转录激活的辅助因子，被HBV显著抑制。
HBV感染后，HMGB1与IFNAR1启动子-3T变异体的结合亲和力降低，因HBV导致的PARP-1表达受抑制而加剧，导致IFNAR1表达进一步减弱。这损害了IFN-α/β的抗病毒和免疫调节作用，进而可能影响HBV感染的临床结局。
