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Updated: Jun 14, 2026

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation
Published on: January 9, 2019
UNC0638 inhibits SARS-CoV-2 entry by blocking cathepsin L maturation
Yongjun Chen1,2, Yujin Shi1,2, Xiaoyan Zuo1,2
1NHC Key Laboratory of System Biology of Pathogens, Christophe Mérieux Laboratory National Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
EHMT2 is a key host factor for SARS-CoV-2 infection. EHMT2 inhibitors block viral entry by preventing cathepsin L maturation, offering a potential strategy for broad-spectrum coronavirus therapies.
Area of Science:
- Virology
- Immunology
- Drug Discovery
Background:
- Viral mutations in SARS-CoV-2 present challenges for antiviral drug development.
- Host post-translational modifications influence interferon responses critical for viral control.
Purpose of the Study:
- To identify host factors essential for SARS-CoV-2 infection using CRISPR-Cas9 screening.
- To investigate the antiviral mechanism of EHMT2 inhibitors.
Main Methods:
- CRISPR-Cas9 screening with adenine base editors to assess 1,278 innate immune genes.
- Pseudovirus assays to evaluate the effect of EHMT2 inhibitor UNC0638 on viral entry.
- Analysis of cathepsin L (CTSL) levels and spike protein cleavage.
Main Results:
- Identified 17 vital host factors, with EHMT2 knockdown showing the strongest antiviral effect.
- EHMT2 inhibitor UNC0638 significantly reduced SARS-CoV-2 endosomal entry across variants.
- UNC0638 decreased mature CTSL, impairing spike protein cleavage and viral membrane fusion.
Conclusions:
- EHMT2 is a host dependency factor for SARS-CoV-2.
- EHMT2 inhibitors block viral entry by inhibiting CTSL maturation, providing a therapeutic strategy.
- EHMT2 inhibitors may serve as pan-coronavirus agents due to CTSL's role in other coronavirus entry.
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