Identification of critical residues in the regulatory protein HBx for Smc5/6 interaction and hepatitis B virus production.

Lili He, Huanyu Shen, Hui Deng, Xiaoyan Zhang, Yang Xu, Chunwei Shi, Zhuqing Ouyang

Antiviral research 2023 Mar

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The host structural maintenance of chromosomes 5/6 complex (Smc5/6) is a restriction factor of hepatitis B virus (HBV) that inhibits the transcription of viral ccDNA. HBV antagonizes this restriction by expressing the regulatory X protein (HBx) which targets Smc5/6 for degradation via DNA damage-binding protein 1 (DDB1) E3 ubiquitin ligase. However, the molecular insights into how Smc5/6 interacts with HBx remain elusive. In this study, we systematically investigated the interaction between Smc5/6 and HBx. Smc5/6 interacts with HBx through multiple sites in the absence of DDB1 in the pull-down assay. HBx C-terminal is sufficient for the interaction. Most importantly, residue Phe132, which is strictly conserved in all HBV subtypes, is critical for interaction with Smc5/6 both in vitro and in vivo. Mutation of this site (F132A) results in defect in Smc5/6 interaction, extrachromosomal reporter transcription, and HBV production both in cells and in mouse model. Collectively, our data identifies a key residue on HBx for Smc5/6 interaction and viral production. These results provide valuable information for both basic research and therapeutic drugs targeting HBx. Copyright © 2023 Elsevier B.V. All rights reserved.

Citation

Lili He, Huanyu Shen, Hui Deng, Xiaoyan Zhang, Yang Xu, Chunwei Shi, Zhuqing Ouyang. Identification of critical residues in the regulatory protein HBx for Smc5/6 interaction and hepatitis B virus production. Antiviral research. 2023 Mar;211:105519