# Ribosomal protein L35 negatively regulates FMDV replication by recruiting AMFR to promote the ubiquitination and degradation of VP2

## TL;DR

This study shows that the ribosomal protein RPL35 helps fight foot-and-mouth disease virus by marking a viral protein for destruction.

## Contribution

The novel finding is that RPL35 recruits AMFR to ubiquitinate and degrade FMDV's VP2 protein, inhibiting viral replication.

## Key findings

- RPL35 interacts with FMDV's VP2 and promotes its K48-linked ubiquitination and degradation.
- Lys217 in VP2 is critical for RPL35's antiviral activity, as shown by the rO-VP2K217R mutant.
- FMDV degrades KPNA3 to block RPL35's nuclear translocation, weakening its antiviral effect.

## Abstract

The control of foot-and-mouth disease virus (FMDV) primarily relies on vaccine immunization; however, this approach is not always fully effective, underscoring the urgent need for novel antiviral strategies. This study identifies RPL35 as a host antiviral protein that targets FMDV. Further mechanistic investigations demonstrate that RPL35 directly interacts with the FMDV structural protein VP2, mediating its K48-linked polyubiquitination and subsequent degradation. The Lys217 residue of VP2 is critical for RPL35’s antiviral activity, as evidenced by the increased viral virulence observed with the rO-VP2K217R mutant virus. Through an unbiased proteomic screen, we revealed that RPL35 recruits the E3 ligase AMFR to ubiquitinate and degrade VP2. Additionally, FMDV induces the degradation of KPNA3, thereby blocking RPL35’s nuclear translocation. This study advances our understanding of host-virus interactions and provides new insights into developing antiviral drugs targeting the ubiquitin-proteasome pathway.

This investigation elucidated the antiviral role of RPL35 in the context of FMDV infection. Our results indicate that RPL35 facilitates the recruitment of AMFR, which, in turn, promotes K48-linked polyubiquitination and subsequent proteasomal degradation of the viral protein VP2. This process thereby mitigates viral infection. Further analysis identified Lys217 of VP2 as a critical ubiquitination site for RPL35, with the inhibitory effect of RPL35 being abolished in the recombinant mutant virus rO-VP2K217R. Additionally, we found that FMDV induces the degradation of KPNA3, which obstructs the nuclear translocation of RPL35. Collectively, these findings suggest that RPL35 functions as a potent antiviral effector in suppressing FMDV infection.