RNA Exosome Complex Regulates Stability of the Hepatitis B Virus X-mRNA Transcript in a Non-stop-mediated (NSD) RNA Quality Control Mechanism.
Hepatitis B virus (HBV) is a stealth virus, minimally inducing the interferon system required for efficient induction of both innate and adaptive immune responses. However, 90% of acutely infected adults can clear the virus, suggesting the presence of other, interferon-independent pathways leading to viral clearance. Given the known ability of helicases to bind viral nucleic acids, we performed a functional screening assay to identify helicases that regulate HBV replication. We identified the superkiller viralicidic activity 2-like (SKIV2L) RNA helicase (a homolog of the Saccharomyces cerevisiae Ski2 protein) on the basis of its direct and preferential interaction with HBV X-mRNA. This interaction was essential for HBV X-mRNA degradation at the RNA exosome. The degradation of HBV X-mRNA at the RNA exosome was also mediated by HBS1L (HBS1-like translational GTPase) protein, a known component of the host RNA quality control system. We found that the redundant HBV-precore translation initiation site present at the 3'-end of HBV X-mRNA (3' precore) is translationally active. The initiation of translation from this site without a proper stop codon was identified by the non-stop-mediated RNA decay mechanism leading to its degradation. Although 3' precore is present in the five main HBV-RNA transcripts, only X-mRNA lacks the presence of an upstream start codons for large, middle, and small (L, M, and S) HBV surface proteins. These upstream codons are in-frame with 3' precore translation initiation site, blocking its translation from the other HBV-mRNA transcripts. To our knowledge, this is the first demonstration of the anti-viral function of the non-stop-mediated RNA decay mechanism.
From the Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan, ahussein@nih.go.jp.
Hussein H
HH
Aly
From the Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.
Junya
J
Suzuki
From the Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan, Department of Applied Biological Science, Tokyo University of Science, Noda 278-8510, Japan, Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan.
Koichi
K
Watashi
Department of Gastroenterology and Metabolism, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan.
Kazuaki
K
Chayama
Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan, and.
Shin-Ichi
S
Hoshino
Laboratory of Human Tumor Viruses, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.
Makoto
M
Hijikata
From the Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.
Takanobu
T
Kato
From the Department of Virology II, National Institute of Infectious Diseases, Tokyo 162-8640, Japan, wakita@nih.go.jp.
Takaji
T
Wakita
D018387:Codon, Initiator / Q000235:genetics / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex / Q000235:genetics / Q000378:metabolism*; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000096:biosynthesis* / Q000235:genetics; D054334:Viral Regulatory and Accessory Proteins
D018387:Codon, Initiator; D012333:RNA, Messenger; D012367:RNA, Viral; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D063326:Exosome Multienzyme Ribonuclease Complex; D004265:DNA Helicases; C114718:SKIV2L protein, human
HBS1L; Non-Stop mediated RNA Decay (NSD); RNA Exosome; RNA degradation; RNA helicase; RNA-binding protein; SKIV2L; exosome complex; hepatitis B virus (HBV, Hep B); virus restriction factor