A Computational Structural Analysis of Host Insertions in the Polyproline Region of the Hepatitis E Virus pORF1 Polyprotein.

Hepatitis E virus, a single-stranded positive-sense RNA virus, is the causative agent of acute viral hepatitis in humans and can lead to chronic infection in immunocompromised individuals. In this setting, strains containing host genome insertions within the polyproline region (PPR) of the pORF1 polyprotein were characterized and shown to display an increased replication rate across all systems. Using in silico modeling of pORF1 across 25 strains, combined with molecular dynamics (MD) simulations, we explored the structural variations caused by these insertions to investigate potential mechanisms underlying the increased replication rate compared to wild-type (WT) strains. Our results showed that the insertions neither induced structural organization within the PPR nor altered its intrinsically disordered nature. MD simulations further demonstrated that the overall stability of pORF1 remained unchanged in strains with insertions compared to WT strains. On the other hand, MD analyses revealed that strains with insertions exhibited an increased number of hydrogen bonds between the PPR and two other domains of pORF1: the MetY domain and the RNA-dependent RNA polymerase (RdRp). The stability of the MetY domain of the strains in the presence of host insertion events was higher than in the WT strains. These additional hydrogen bonds could position the MetY domain and the RdRp closer together, potentially promoting more efficient viral RNA synthesis. Validation of this hypothesis will require experimental structural studies, as well as computational modeling of the proposed dodecameric pORF1 structure.