# Cellular eEF1G Inhibits Porcine Deltacoronavirus Replication by Binding Nsp12 and Disrupting Its Interaction with Viral Genomic RNA

## TL;DR

This study shows that the host protein eEF1G inhibits the replication of porcine deltacoronavirus by disrupting its key viral enzyme's interaction with RNA.

## Contribution

eEF1G is identified as a novel host restriction factor that inhibits PDCoV replication by competing with Nsp12 for RNA binding.

## Key findings

- eEF1G directly interacts with PDCoV Nsp12 and binds to viral genomic RNA.
- eEF1G knockdown increases viral replication and negative-stranded RNA synthesis.
- eEF1G disrupts the Nsp12-RNA interaction, impairing RdRp activity.

## Abstract

Porcine deltacoronavirus (PDCoV) is an emerging pathogen that causes severe, often fatal, diarrhea in suckling piglets and has zoonotic potential. Its nonstructural protein 12 (Nsp12), functioning as the RNA-dependent RNA polymerase (RdRp), is a central component of the viral replication–transcription complex and a critical target for host antiviral mechanisms. Here, we identified eukaryotic elongation factor 1 gamma (eEF1G) as a host interactor of PDCoV Nsp12 by immunoprecipitation-coupled mass spectrometry in IPEC-J2 cells. This interaction was confirmed by co-immunoprecipitation, pull-down assays, and confocal microscopy. Functional analyses involving siRNA knockdown and overexpression of eEF1G, combined with viral titration, strand-specific real-time quantitative PCR, and RNA immunoprecipitation assays, demonstrated that eEF1G directly binds to Nsp12. Knockdown of eEF1G significantly enhanced viral replication and increased negative-stranded RNA synthesis, whereas overexpression did not affect viral proliferation. Furthermore, eEF1G was found to bind PDCoV genomic RNA and competitively disrupt the interaction between Nsp12 and viral RNA, thereby impairing RdRp activity. Our results indicate that eEF1G acts as a novel host restriction factor that inhibits PDCoV replication by competing with Nsp12 for genomic RNA binding, ultimately blocking negative-stranded RNA synthesis. This study unveils a new antiviral mechanism and highlights a potential target for developing interventions against PDCoV.