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bioRxiv · 10.1101/2025.11.11.685253

Structural and Functional Insights into HBx-Smc6 Targeting for HBV Inhibition

Cheng, T.·Zhou, J.·Huang, W.·Du, L.·He, P.·Yang, R.·Gao, Y.·Hao, M.·Hu, K.·Chen, J.·Wang, H.·Rao, Z.·Yuan, Z.·Wang, L.
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Abstract

The hepatitis B virus (HBV) X protein (HBx) is a multifunctional regulator essential for HBV replication and HBV-associated hepatocarcinogenesis. Despite its central role, the molecular basis of HBx function has remained elusive. Here, we present the first cryo-electron microscopy structure of the human HBx-CRL4-Smc5/6 complex at 3.1 [A] resolution. In this reconstituted ten-subunit assembly, HBx adopts a Zn2 {square}-stabilized Y-shaped architecture that simultaneously engages the DDB1 and the Smc6 subunit. A composite helix-turn-helix (HTH) pocket in HBx accommodates a conserved "Leucine Key" motif (LRCKL) on Smc6, forming a critical interface essential for complex stability and function. Molecular docking and biochemical validation reveal that the compound Tranilast binds this HTH pocket, disrupts the HBx-Smc6 interaction, and suppresses HBV replication. These findings define the structural mechanism by which HBx counteracts host restriction and establish the HBx-Smc6 interface as a previously unrecognized and druggable target for antiviral intervention.

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Cheng, T., Zhou, J., Huang, W., Du, L., He, P., Yang, R., Gao, Y., Hao, M., Hu, K., Chen, J., Wang, H., Rao, Z., Yuan, Z., Wang, L.. 2025-11-12. Structural and Functional Insights into HBx-Smc6 Targeting for HBV Inhibition. https://doi.org/10.1101/2025.11.11.685253

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