# Cellular sensor DAP5 decodes Betacoronaviral NSP5 to drive virus-induced senescence

## TL;DR

The protein DAP5 helps cells detect SARS-CoV-2 infection and switch from apoptosis to senescence, aiding viral replication.

## Contribution

Identifies DAP5 and its cleavage by SARS-CoV-2 NSP5 as a mechanism triggering virus-induced senescence.

## Key findings

- DAP5 is cleaved by SARS-CoV-2 NSP5 to produce DAP51–451, which initiates cellular senescence.
- DAP51–451 interacts with p53 and activates NF-κB to promote senescence and SASP factors.
- TRIM7 degrades DAP51–451 via ubiquitination, limiting viral replication.

## Abstract

Viral infection induces host cells to enter a state of “virus-induced senescence (VIS)”, which provides a stable cellular environment for viral replication. However, it is unclear about the molecular mechanism of this process. Here, we identified cellular protein DAP5 and its N-terminal fragment DAP51–451 as sensors to viral infection.

Upon SARS-CoV-2 infection, cellular apoptosis and senescence levels were assessed. This led to the identification of DAP5 as a pivotal proteolytic substrate that links viral protease activity to host cell fate determination. The specific cleavage site on DAP5 targeted by the non-structural protein 5 (NSP5) encoded by SARS-CoV-2 was mapped using Western Blot and Fluorescence Resonance Energy Transfer (FRET) analysis. The functional role of the resulting N-terminal fragment DAP51–451 was then characterized through a series of molecular biology experiments, including ChIP-seq, dual-luciferase reporter assays, and co-immunoprecipitation (Co-IP). Furthermore, ubiquitination assays and protein stability analyses were conducted to delineate the degradation pathway responsible for clearing this N-terminal fragment DAP51-451.

Viral infection-activated caspase 3 cleaves DAP5, which contributed to positive feedback loops, reinforcing apoptotic process. NSP5 interrupted the apoptotic process by NSP5-specific cleavage of DAP5 that led to the production of the N-terminal fragment DAP51-451, which initiated the cellular senescence program, achieving an “apoptosis→senescence” fate transformation and thereby promoting viral replication of SARS-CoV-2. Mechanistically, DAP51–451 interacted with the transcription factor p53 to enter the nucleus and bind to CDKN1A locus to increase its expression, thereby triggering cell cycle arrest. Additionally, DAP51–451 activated the NF-κB signaling pathway and promoted the production of senescence-associated secretory phenotype (SASP) factors. E3 ubiquitin ligase TRIM7 encoded by host cells degraded the N-terminal fragment DAP51–451 by Glutamine C-degron-mediated ubiquitination and protein degradation, and restricted viral replication.

Our findings clarify the mechanism of SARS-CoV-2 induced VIS and establish a model of host cells inhibiting VIS through protein degradation and limiting viral replication, which provides a basis for subsequent immunological studies of emergent pathogenic microbial infection.