PARP3 Promotes SARS-CoV-2 Replication via Interaction with the Viral Nucleocapsid Protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exploits host cellular machinery to support its replication. Members of the host poly(ADP-ribose) polymerase (PARP) family regulate the DNA damage response and have been implicated in both antiviral and proviral processes. In this study, we investigated the potential role of PARP3 in SARS-CoV-2 replication in VeroE6/Rep3 cells. siRNA-mediated knockdown of PARP3 reduced viral subgenomic RNA (sgRNA) levels and reporter activity, whereas PARP3 overexpression enhanced these processes, suggesting that PARP3 promotes SARS-CoV-2 replication. In addition, PARP3 expression was increased in SARS-CoV-2-infected Calu-3 cells and in cells expressing SARS-CoV-2 nucleocapsid protein, suggesting that the nucleocapsid protein contributes to PARP3 upregulation during infection. Co-immunoprecipitation and immunofluorescence analyses revealed that PARP3 associates with the nucleocapsid protein and redistributes to the cytoplasm in nucleocapsid-expressing cells. Screening of a PARP inhibitor library identified venadaparib as a compound that reduced SARS-CoV-2 sgRNA levels and reporter activity in VeroE6/Rep3 cells with limited cytotoxicity under the condition tested. We further found that venadaparib reduced the interaction between PARP3 and the nucleocapsid protein. Molecular docking analysis further suggested that venadaparib can bind to the PARP3 catalytic domain. Collectively, these findings support a model in which PARP3 facilitates SARS-CoV-2 replication through its interaction with the viral nucleocapsid protein and suggest that venadaparib warrants further evaluation as a host-directed antiviral candidate.