Systematic identification of anti-interferon function on hepatitis C virus genome reveals p7 as an immune evasion protein.
Hepatitis C virus (HCV) encodes mechanisms to evade the multilayered antiviral actions of the host immune system. Great progress has been made in elucidating the strategies HCV employs to down-regulate interferon (IFN) production, impede IFN signaling transduction, and impair IFN-stimulated gene (ISG) expression. However, there is a limited understanding of the mechanisms governing how viral proteins counteract the antiviral functions of downstream IFN effectors due to the lack of an efficient approach to identify such interactions systematically. To study the mechanisms by which HCV antagonizes the IFN responses, we have developed a high-throughput profiling platform that enables mapping of HCV sequences critical for anti-IFN function at high resolution. Genome-wide profiling performed with a 15-nt insertion mutant library of HCV showed that mutations in the p7 region conferred high levels of IFN sensitivity, which could be alleviated by the expression of WT p7 protein. This finding suggests that p7 protein of HCV has an immune evasion function. By screening a liver-specific ISG library, we identified that IFI6-16 significantly inhibits the replication of p7 mutant viruses without affecting WT virus replication. In contrast, knockout of IFI6-16 reversed the IFN hypersensitivity of p7 mutant virus. In addition, p7 was found to be coimmunoprecipitated with IFI6-16 and to counteract the function of IFI6-16 by depolarizing the mitochondria potential. Our data suggest that p7 is a critical immune evasion protein that suppresses the antiviral IFN function by counteracting the function of IFI6-16.
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095.
Hangfei
H
Qi
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095.
Virginia
V
Chu
Molecular Biology Institute, University of California, Los Angeles, CA 90095.
Nicholas C
NC
Wu
Department of Human Genetics, University of California, Los Angeles, CA 90095.
Zugen
Z
Chen
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095.
Shawna
S
Truong
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095.
Gurpreet
G
Brar
Institute of Biomedical Informatics, National Yang-Ming University, Taipei, 112 Taiwan.|Bioinformatics Program, Taiwan International Graduate Program, Institute of Information Science, Academia Sinica, Taipei, 115 Taiwan.|Institute of Information Science, Academia Sinica, Taipei, 115 Taiwan.
Sheng-Yao
SY
Su
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095.|Cancer Institute, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, UCLA-ZJU Joint Center for Medical Education and Research, Zhejiang University School of Medicine, Hangzhou 310003, China.
Yushen
Y
Du
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095.
Vaithilingaraja
0000-0002-6872-5118
V
Arumugaswami
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095.
C Anders
CA
Olson
Institute of Information Science, Academia Sinica, Taipei, 115 Taiwan.
Shu-Hua
SH
Chen
Institute of Information Science, Academia Sinica, Taipei, 115 Taiwan.
Chung-Yen
CY
Lin
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095.
Ting-Ting
TT
Wu
Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095; rsun@mednet.ucla.edu.|Molecular Biology Institute, University of California, Los Angeles, CA 90095.|Cancer Institute, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, UCLA-ZJU Joint Center for Medical Education and Research, Zhejiang University School of Medicine, Hangzhou 310003, China.
Ren
R
Sun
D064113:CRISPR-Cas Systems; D002460:Cell Line; D020869:Gene Expression Profiling; D055786:Gene Knockout Techniques; D015723:Gene Library; D016679:Genome, Viral; D016174:Hepacivirus / Q000235:genetics / Q000472:pathogenicity*; D006526:Hepatitis C / Q000276:immunology* / Q000821:virology; D054884:Host-Pathogen Interactions / Q000276:immunology*; D006801:Humans; D057131:Immune Evasion; D007113:Immunity, Innate; D007372:Interferons / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008099:Liver / Q000276:immunology / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000276:immunology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D015398:Signal Transduction; D014764:Viral Proteins / Q000235:genetics / Q000276:immunology*; D014779:Virus Replication; D000086082:Viroporin Proteins
D007372:Interferons; D024101:Mitochondrial Proteins; D014764:Viral Proteins; C468762:IFI6 protein, human; C088369:p7 protein, Hepatitis C virus; D000086082:Viroporin Proteins
HCV; IF6-16 antiviral function; high-throughput mutagenesis; innate immune evasion mechanism; p7 ion channel protein