Hepatitis B virus(HBV)is regarded as a stealth virus,invading and replicating efficiently in human liver undetected by host innate antiviral immunity.Here,we show that type I interferon(IFN)induction but not its downstream signaling is blocked by HBV replication in HepG2.2.15 cells.This effect may be partially due to HBV X protein(HBx),which impairs IFNβ promoter activation by both Sendai virus(SeV)and components implicated in signaling by viral sensors.As a deubiquitinating enzyme(DUB),HBx cleaves Lys63-linked polyubiquitin chains from many proteins except TANK-binding kinase 1(TBK1).It binds and deconjugates retinoic acid-inducible gene I(RIG I)and TNF receptor-associated factor 3(TRAF3),causing their dissociation from the downstream adaptor CARDIF or TBK1 kinase.In addition to RIG I and TRAF3,HBx also interacts with CARDIF,TRIF,NEMO,TBK1,inhibitor of kappa light polypeptide gene enhancer in B-cells,kinase epsilon(IKKi)and interferon regulatory factor 3(IRF3).Our data indicate that multiple points of signaling pathways can be targeted by HBx to negatively regulate production of type I IFN.