A DNA-based non-infectious replicon system to study SARS-CoV-2 RNA synthesis

Area of Science:

• Virology
• Molecular Biology
• Infectious Diseases

Background:

• The COVID-19 pandemic necessitates understanding SARS-CoV-2 pathogenesis.
• High-containment laboratories (BSL-3) limit research progress.
• A safer alternative for studying SARS-CoV-2 replication is needed.

Purpose of the Study:

• To develop a bio-safe SARS-CoV-2 replication and transcription system.
• To investigate the role of the nucleocapsid (N) protein in viral RNA synthesis.
• To evaluate the utility of the system for antiviral drug screening.

Main Methods:

• Utilized a bacterial artificial chromosome (BAC) method to create a SARS-CoV-2 replicon in Vero E6 cells.
• Implemented an improved real-time quantitative reverse transcription PCR (RT-qPCR) for RNA analysis.
• Assessed the impact of N protein mutations and antiviral drugs on replicon activity.

Main Results:

• Established a SARS-CoV-2 replicon system that avoids infectious virion formation.
• Demonstrated that the SARS-CoV-2 nucleocapsid (N) protein enhances subgenomic RNA (sgRNA) transcription.
• Identified specific N protein mutations (R203K, S194L) that increase transcription levels.
• Showed that remdesivir and chloroquine inhibit the replicon's transcription.

Conclusions:

• Developed a bio-safe and effective SARS-CoV-2 replicon system for research.
• The N protein plays a crucial role in SARS-CoV-2 RNA transcription.
• The system shows promise for studying viral mechanisms and screening antiviral drugs.