Translatomic profiling reveals novel self-restricting virus-host interactions during HBV infection.

Abstract Background and Aims Hepatitis B Virus remains to be yet unresolved global threat to human health. It remains incompletely understood how HBV self-restricts in host during most adulthood infections, and multi-omics analyses were performed to systematically interrogate into HBV-host interaction and the life cycle of HBV. Methods RNA-sequencing and ribosome profiling were conducted with cell-based models for HBV replication and gene expression. The novel translational events or products hereby detected were then characterized, and functionally assessed in both cell and mouse models. Moreover, quasi-species analyses of HBV subpopulations were conducted with patients at immune tolerance or activation phases, using next- or third-generation sequencing. Results We identified EnhI-SL (Enhancer I-stem loop) as a new cis element in HBV genome, and the mutations disrupting EnhI-SL were found to elevate viral polymerase expression. Furthermore, while re-discovering HpZ/P’, a previously under-explored isoform of HBV polymerase, we also identified HBxZ as a novel short isoform of HBX and confirmed their existence and functionally characterized them as potent suppressors for HBV gene expression or genome replication. Mechanistically, HpZ/P’ was found to repress HBV gene expression partially through interacting with, and sequestering SUPV3L1. The abundances of the HBV mutants either deficient of HpZ/P’ or disrupted in EnhI-SL seemed to be diminished upon the activation of host immune system. Finally, SRSF2, a HBV-down-regulated host protein in RNA spliceosome, was found to promote the splicing of viral pre-genomic RNA and HpZ/P’ biogenesis. Conclusion This study has identified multiple viral self-restricting mechanisms in HBV-host interaction. Particularly, SRSF2-HpZ/P’ appeared to constitute another negative feedback mechanism in controlling HBV life-cycle. Targeting host splicing machinery might thus represent a yet under-explored strategy to intervene into HBV-host interaction.