# UBXN7 facilitates SARS-CoV-2 replication via inhibiting the K48-linked ubiquitination of viral N protein

## TL;DR

UBXN7 helps SARS-CoV-2 and other human coronaviruses replicate by preventing the breakdown of a key viral protein.

## Contribution

UBXN7 is identified as a new host factor that promotes coronavirus replication by inhibiting N protein ubiquitination.

## Key findings

- UBXN7 promotes SARS-CoV-2 replication by inhibiting K48-linked ubiquitination of the N protein.
- UBXN7 interacts with the N protein via its UBX domain and prevents its proteasomal degradation.
- K257 on the N protein is a critical target site for UBXN7, essential for viral genome assembly.

## Abstract

Host factor-mediated post-translational modification of coronavirus proteins has been demonstrated as an important strategy for regulating viral proliferation. Identification of key host genes involved in this process may provide potential therapeutic targets. In this study, we used the complementary reverse genetic system to determine that UBXN7 promotes SARS-CoV-2 viral double-stranded RNA (dsRNA) production and also promotes the replication of other human coronaviruses. However, UBXN7 does not affect the replication of VSV and RSV, suggesting that it may be a potential pan human coronaviral anti-infection target. Our results revealed that UBXN7 did not affect the viral invasion of cells, but instead hijacked viral genome assembly by interacting with SARS-CoV-2 N protein via its UBX domain. Further data indicated that UBXN7 inhibits K48-linked ubiquitination and proteasomal degradation of SARS-CoV-2 N protein, leading to N protein accumulation. Moreover, K257 of N protein was identified as specific target site of UBXN7 which are critical for viral replication. These findings reveal a novel relationship between host gene-mediated protein ubiquitylation and viral genome assembly, providing new strategies for potential pan-coronavirus drug design.

Coronaviruses, including SARS-CoV-2, rely on host cellular machinery to complete their life cycle. Here, we identify UBXN7, a host ubiquitin-regulatory protein, as a critical facilitator of SARS-CoV-2 and other human coronaviruses. UBXN7 promotes viral replication by directly binding to the viral nucleocapsid (N) protein through its UBX domain, thereby inhibiting K48-linked polyubiquitination of the N protein. This interaction prevents proteasomal degradation of the N protein, allowing its accumulation and enhancing its ability to bind viral genomic RNA—a key step in virion assembly. Strikingly, UBXN7 specifically targets conserved lysine residue K257 on the N protein, which are essential for viral genome assembly. Importantly, UBXN7’s proviral role is selective, as it does not influence the replication of unrelated viruses like VSV or RSV. Our findings uncover a novel mechanism by which coronaviruses hijack host ubiquitination pathways to stabilize viral proteins and drive infection. Targeting the UBXN7-N protein axis could offer a promising strategy for developing broad-spectrum antivirals against current and emerging coronaviruses.