title: Autophagy machinery impaired interferon signalling pathways to benefit hepatitis B virus replication.
abstract: BACKGROUND
  Autophagy-related genes ATG4B, ATG7, and ATG12 have been identified to play a critical role in viral replication. However, these genes have yet to be identified in hepatitis B virus (HBV).
  
  
  OBJECTIVE
  To characterise the role of ATG4B, ATG7, and ATG12 genes in HBV infection.
  
  
  METHODS
  The mRNA expression was examined by quantitative real-time RT-PCR and Western blotting. Short hairpin RNA (shRNA) of the target gene was used to examine the function of the gene in HBV replication. Evaluation of HBV DNA level was performed by real-time PCR.
  
  
  RESULTS
  Our findings revealed that ATG12 gene expression was significantly up-regulated (p < 0.005), whereas ATG7 gene expression was down-regulated (p < 0.0001) in HepG2.2.15 cells when compared to HepG2 cells. However, no significant difference in mRNA level of ATG4B was observed. These results were consistent with protein level findings. Moreover, we analysed the function of ATG12 in HBV replication by using ATG12 shRNA and evaluated HBV DNA level. We found that the amount of HBV was decreased in ATG12-knockdown HepG2.2.15 cells when compared to control HepG2.2.15 cells (P < 0.05). The mRNA expression of interferon-alpha (IFN-α), interferon-beta (IFN-β), and interferon-inducible genes (IFI) was also investigated. Our results showed that the expression of IFN-α, IFN-β, and IFI27 genes were increased in ATG12-knockdown cells but not in Mx1 gene when compared to control cells (p < 0.005, p < 0.0001 and p < 0.005, respectively).
  
  
  CONCLUSIONS
  These autophagy-related genes, ATG12 may play a role in HBV replication via impairing IFN pathway. However, the biological significance of other autophagic genes such as ATG7 warrants further study.
authors.affiliation: Department of Microbiology, Faculty of Science, Kasetsart University, Bangkok, Thailand.
authors.forename: Areerat
authors.initials: A
authors.lastname: Kunanopparat
authors.forename: Nattiya
authors.initials: N
authors.lastname: Hirankarn
authors.forename: Chaivat
authors.initials: C
authors.lastname: Kittigul
authors.forename: Pisit
authors.initials: P
authors.lastname: Tangkijvanich
authors.forename: Ingorn
authors.initials: I
authors.lastname: Kimkong
mesh_terms: D001343:Autophagy; D000071192:Autophagy-Related Protein 12; D000071193:Autophagy-Related Protein 7; D004279:DNA, Viral / Q000032:analysis; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000502:physiology*; D006801:Humans; D007372:Interferons / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000502:physiology; D044764:Ubiquitin-Activating Enzymes / Q000502:physiology; D014779:Virus Replication
chemical_list: C466624:ATG12 protein, human; D000071192:Autophagy-Related Protein 12; D004279:DNA, Viral; D025841:Small Ubiquitin-Related Modifier Proteins; D007372:Interferons; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes