Hepatitis B Virus X Protein Promotes Degradation of SMC5/6 to Enhance HBV Replication.
The hepatitis B virus (HBV) regulatory protein X (HBx) activates gene expression from the HBV covalently closed circular DNA (cccDNA) genome. Interaction of HBx with the DDB1-CUL4-ROC1 (CRL4) E3 ligase is critical for this function. Using substrate-trapping proteomics, we identified the structural maintenance of chromosomes (SMC) complex proteins SMC5 and SMC6 as CRL4(HBx) substrates. HBx expression and HBV infection degraded the SMC5/6 complex in human hepatocytes in vitro and in humanized mice in vivo. HBx targets SMC5/6 for ubiquitylation by the CRL4(HBx) E3 ligase and subsequent degradation by the proteasome. Using a minicircle HBV (mcHBV) reporter system with HBx-dependent activity, we demonstrate that SMC5/6 knockdown, or inhibition with a dominant-negative SMC6, enhance HBx null mcHBV-Gluc gene expression. Furthermore, SMC5/6 knockdown rescued HBx-deficient HBV replication in human hepatocytes. These results indicate that a primary function of HBx is to degrade SMC5/6, which restricts HBV replication by inhibiting HBV gene expression.
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Christopher M
CM
Murphy
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Yanping
Y
Xu
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Feng
F
Li
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Kouki
K
Nio
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Natalia
N
Reszka-Blanco
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Xiaodong
X
Li
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Yaxu
Y
Wu
J. Craig Venter Institute, 9714 Medical Center Drive, Rockville, MD 20850, USA.
Yanbao
Y
Yu
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Electronic address: yxiong@email.unc.edu.
Yue
Y
Xiong
Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Electronic address: lsu@med.unc.edu.
Lishan
L
Su
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone; D015967:Gene Expression Regulation, Viral; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006509:Hepatitis B / Q000378:metabolism / Q000473:pathology / Q000821:virology; D006515:Hepatitis B virus / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D022781:Hepatocytes / Q000378:metabolism / Q000821:virology; D006801:Humans; D008099:Liver / Q000473:pathology / Q000821:virology; D051379:Mice; D011485:Protein Binding; D059748:Proteolysis; D040901:Proteomics; D013379:Substrate Specificity; D015534:Trans-Activators / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination; D054334:Viral Regulatory and Accessory Proteins; D014779:Virus Replication / Q000502:physiology*; D053722:Receptors, Interleukin-17
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D015534:Trans-Activators; D044767:Ubiquitin-Protein Ligases; D054334:Viral Regulatory and Accessory Proteins; C408922:IL17RB protein, human; D053722:Receptors, Interleukin-17; C432931:SMC5 protein, human; C432932:SMC6 protein, human; C057628:hepatitis B virus X protein