Recently, a study used MHV as a model coronavirus demonstrated that in human lung cell lines, the infection of SARS-CoV-2 strikingly upregulated the noncanonical MARylating PARP isozymes including PARP7, PARP9, PARP10, PARP11, PARP12, PARP13, and PARP14, and then depressed the cellular NAD metabolome by inducing the expression of enzymes for salvage NAD synthesis from nicotinamide (NAM) and nicotinamide riboside (NR), and reducing other NAD biosynthetic (56). Here, PARP1 is linked to infection.