# Nuclear shuttling of CDC4 mediated broad-spectrum antiviral activity against diverse coronaviruses

## TL;DR

This study shows that the CDC4 protein can block the replication of multiple coronaviruses, including PDCoV, by interfering with viral proteins that suppress the immune response.

## Contribution

The study reveals CDC4's novel role in antiviral defense by inhibiting coronavirus nucleocapsid proteins from suppressing immune signaling.

## Key findings

- CDC4 suppresses PDCoV replication by disrupting the interaction between the viral N protein and RIG-I.
- CDC4 exhibits broad-spectrum antiviral activity against diverse coronaviruses like TGEV and SARS-CoV-2.
- The antiviral mechanism involves CDC4 competing with viral N proteins to prevent immune signaling suppression.

## Abstract

Pandemics of coronavirus (CoV)-related infection have been a major issue since the outbreaks of SARS, MERS and COVID-2019 in the past decades, leading a substantial threat to public health. Porcine deltacoronavirus (PDCoV), a new swine coronavirus, causes enteropathogenic disease characterized by acute diarrhoea, vomiting and dehydration in suckling piglets and poses potential risks of cross-species transmission. Here we reveal a novel function of CDC4 protein in restricting PDCoV infection. Ectopic expression of CDC4 suppresses PDCoV replication, whereas knockdown of CDC4 expression enhances PDCoV infection. Importantly, it was revealed that PDCoV encoded nucleocapsid (N) was involved in CDC4 nuclear-cytoplasmic shuttling, which was critical for CDC4 to exert the antiviral activity against PDCoV replication. Mechanistically, PDCoV N protein was detected to specifically interact with RIG-I to antagonize RIG-I-like receptor (RLR)-mediated IFN-β production, leading to disruptions of host innate immune defense. Meanwhile, CDC4 was proved to interact with PDCoV N protein and disrupted the interaction between PDCoV N and RIG-I, resulting in alleviated antagonism of IFN-β production mediated by PDCoV N. Similarly, a broad-spectrum inhibitory effects of CDC4 on N mediated antagonism were confirmed by the shared mechanisms among the different coronaviruses from Coronaviridae family, such as transmissible gastroenteritis virus (TGEV) from Alphacoronavirus (α-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from Betacoronavirus (β-CoV). Therefore, a novel antiviral role of CDC4 was elucidated that CDC4 competes binding with CoVs N proteins to suppress CoVs N mediated antagonism of RLR associated signalling pathway in the context of diverse coronavirus infections.