TIP60 Complex Inhibits Hepatitis B Virus Transcription

Hepatitis B virus (HBV) is a global major health problem, with over one million deaths annually caused by chronic liver damage. Understanding host factors that modulate HBV replication may aid the development of anti-HBV therapies. Our recent genome-wide small interfering RNA screen using recombinant HBV demonstrated that TIP60 inhibited HBV infection. Here, we show that TIP60 complex contributes to anti-HBV defense. The TIP60 complex bound to the HBV promoter and suppressed HBV transcription driven by the precore/core promoter. The silencing of EP400, TRRAP, BAF53a, RUVBL1, and RUVBL2, which form the TIP60 complex, also resulted in increased HBV transcription. These results contribute to our enhanced understanding of the molecular mechanism of HBV transcription associated with the chromatin structure of HBV covalently closed circular DNA (cccDNA). Exploiting these intrinsic cellular defenses might help develop new anti-HBV agents. IMPORTANCE Investigating the molecular mechanism of HBV replication is important to understand the persistent nature of HBV infection and to aid the development of new HBV agents, which are currently limited to HBV polymerase inhibitors. Previously, we developed a new reporter HBV. By screening host factors using this recombinant virus, we identified several gene products that regulate HBV infection, including TIP60. Here, we showed that TIP60, a catalytic subunit of the NuA4 complex, inhibited HBV replication. Depletion of TIP60 increased the level of HBV mRNA. Moreover, TIP60 localized in the HBV cccDNA chromatin complex catalyzed the acetylation of histone H4 to recruit Brd4. These results suggest that TIP60, in concert with other cellular factors, plays an important role in the regulation of the HBV chromatin structure by acting as a critical component of the intrinsic antiviral defense, which sheds new light on the regulation of HBV replication.