Functional dissection of an IFN-alpha/beta receptor 1 promoter variant that confers higher risk to chronic hepatitis B virus infection.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Zhou
Jie
J
Department of Microbiology, Research Centre of Infection and Immunology, The University of Hong Kong, Pokfulam, Hong Kong.
Huang
Jian-Dong
JD
Poon
Vincent K M
VK
Chen
Ding-Qiang
DQ
Chan
Chris C S
CC
Ng
Fai
F
Guan
Xin-Yuan
XY
Watt
Rory M
RM
Lu
Liwei
L
Yuen
Kwok-Yung
KY
Zheng
Bo-Jian
BJ
D000483:Alleles; D001483:Base Sequence; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D015536:Down-Regulation; D020022:Genetic Predisposition to Disease; D024243:HMGB1 Protein / Q000378:metabolism; D019694:Hepatitis B, Chronic / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011379:Prognosis; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053633:Receptor, Interferon alpha-beta / Q000235:genetics*; D012307:Risk Factors; D015533:Transcriptional Activation; D014162:Transfection
D017931:DNA Primers; D024243:HMGB1 Protein; C507964:IFNAR1 protein, human; D012333:RNA, Messenger; D053633:Receptor, Interferon alpha-beta; D004247:DNA; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases