# Tandemly Repeated G-Quadruplex Structures in the Pseudorabies Virus Genome: Implications for Epiberberine-Based Antiviral Therapy

## TL;DR

This study identifies G-quadruplex structures in the Pseudorabies virus genome and shows that a natural compound can inhibit viral replication by targeting these structures.

## Contribution

The discovery of tandemly repeated G4 structures in the PRV genome and their antiviral targeting by epiberberine is novel.

## Key findings

- Two G4 structures (R1 and R2) were identified and confirmed in the PRV genome.
- Epiberberine stabilizes these G4 structures and inhibits Taq polymerase progression and viral replication.
- In vivo, epiberberine improved survival and reduced viral load in multiple organs of infected mice.

## Abstract

G-quadruplex (G4) structures have emerged as critical regulatory elements in viral genomes and represent potential targets for antiviral intervention. In this study, we identified and characterized G4 structures in the unique long (UL) region of the Pseudorabies virus (PRV) genome, highlighting their role as novel antiviral targets. Bioinformatic analysis revealed two guanine-rich regions (R1 and R2) that form stable G4 structures, as confirmed by fluorescence assays, circular dichroism (CD) spectroscopy, and immunofluorescence staining. Notably, these G4 structures exhibit a tandem repeat arrangement, a previously unreported feature in the PRV genome. Epiberberine (EPI), a natural G4-stabilizing ligand, bound to and stabilized these structures, leading to the inhibition of Taq polymerase progression. Functional assays demonstrated that EPI effectively suppressed PRV replication in vitro while having no significant impact on viral entry or release. In vivo, EPI treatment significantly improved survival rates and reduced viral loads in multiple organs, including the brain, heart, lungs, and kidneys of infected mice. These findings provide new insights into the role of G4 structures in PRV replication and demonstrate that EPI exhibits potential antiviral activity by targeting G4 structures.