The coronavirus macrodomain is required to prevent PARP-mediated inhibition of virus replication and enhancement of IFN expression
(A,B) BMDMs were transfected with control siRNA (siCtl) or PARP-specific siRNA as described in Methods. Approximately 28 hours later, cells were infected with WT or N1347A MHV and collected at 18–22 hpi. RNA levels were determined by RT-qPCR (A), and viral titers were determined by plaque assay (B). The data in (A) represent the combined results of two to five experiments; n = 9 for siPARP7, n = 6 for siPARP9, n = 6 for siPARP10, n = 12 for siPARP11, n = 15 for siPARP12.2, n = 9 for siPARP12.3, n = 12 for siPARP14.1, n = 12 for siPARP14.2. The results in (B) show one experiment representative of two independent experiments. (C) PARP14-/- or PARP14+/- littermate control BMDMs were infected with WT or N1347A virus, cells were collected at 15 hpi, and gRNA levels were determined by RT-qPCR. The data in (C) show one experiment representative of four independent experiments. (D) Structure of PARP14 inhibitor compound 8K. (E) BMDMs were infected with WT or N1347A virus and treated with 5 μM compound 8K or vehicle (DMSO) following a 1-hour adsorption phase. Cells were collected at 18 hpi, and gRNA levels were determined by RT-qPCR. The data in (E) represent the combined results of four experiments; n = 12. Numbers above bars represent fold difference between WT and N1347A or between siPARP/siCtl or inhibitor/DMSO-treated cells infected with N1347A virus.