Phosphorylation-Dependent Modulation of HBV Nuclear Import: Insights from Molecular Dynamics Simulations

• Juan Felipe Marin, Biochemistry, Universidad Nacional de Colombia

• Jodi Hadden-Perilla, Chemistry and Biochemistry, University of Delaware

Hepatitis B virus (HBV) attacks the human liver, and chronic infection can lead to diseases like cancer and cirrhosis. The capsid of HBV contains a Nuclear Localization Signal (NLS) in its C-terminal domain recognized by importin ⍺, a pivotal protein involved in transporting cargo into the cell nucleus. Understanding the interaction between the HBV NLS and importin ⍺ holds significant potential for gaining insights into the molecular mechanisms governing viral infection and replication.

Existing literature indicates that phosphorylation of the HBV C-terminal domain may be important for nuclear import, but molecular dynamics (MD) simulations suggest that phosphorylation at major sites, particularly SER170, could obstruct the NLS and disrupt importin ⍺ binding. We hypothesize that phosphorylation at minor sites, particularly SER168 and SER176, could instead promote NLS binding to importin ⍺. MD simulations are performed for four systems: without phosphorylation, and phosphorylated at SER168, SER170, and SER176, respectively.

We analyze the frequency of hydrogen bonds in each system and use MM-GBSA to calculate the binding free energies to determine the strength of the NLS-importin ⍺ complex. These investigations will shed light on the role of phosphorylation in nuclear import and could offer valuable insights for understanding viral replication mechanisms and potential therapeutic targets.