Construction and validation of a cell based reporter assay for identifying inhibitors of SARS coronavirus 2 RNA dependent RNA polymerase activity

초록

Targeting RNA-dependent RNA polymerase (RdRp), a highly conserved enzyme essential for SARS coronavirus 2 (SARS-CoV-2) replication and transcription, represents a promising antiviral strategy due to its lower mutation rate than structural proteins such as Spike. This study introduces a cell-based assay system for screening potential SARS-CoV-2 RdRp inhibitors, contributing to ongoing efforts to identify effective antiviral agents. The assay utilizes a reporter vector containing the 3 ' untranslated region (UTR), luciferase reporter gene, and 5' UTR gene, sequentially arranged in reverse under the control of the cytomegalovirus promoter in the pcDNA3.1 vector. Co-transfection with SARS-CoV-2 RdRp resulted an increase in luminescence-based quantification of RdRp activity, achieving a Z-factor of 0.605, indicative of high reproducibility and reliability for high-throughput screening. Established RdRp inhibitors, including remdesivir, molnupiravir, tenofovir, and sofosbuvir, significantly reduced reporter activity, with remdesivir exhibiting the strongest inhibition. A newly identified RdRp inhibitor was further validated through primer extension polymerase and NMPylation assays, along with virus-based experiments, confirming its inhibitory mechanism. These results highlight the utility of this screening system in identifying effective RdRp-targeting antivirals, reinforcing the strategic importance of RdRp inhibition in combating SARS-CoV-2 and emerging variants.

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