FIG 2.
Conservation of coronavirus 3CLpro activity enables CoV protease reporter compatibility with many coronaviruses. (A) Phylogenetic tree of five coronaviruses, SARS-CoV-2, SARS-CoV, murine hepatitis virus (MHV), avian infectious bronchitis virus (IBV), and HCoV-229E, generated based on the polyprotein ORF1ab using NCBI Virus (34). These viruses span three coronavirus groups: Alphacoronavirus, Betacoronavirus, and Gammacoronavirus. 3CLpro protein sequence identities are compared to the SARS-CoV-2 3CLpro. (B) Microscopy of 293T cells 48 h after transfection with CoV reporter 3 and coronavirus 3CLpro proteins or an influenza virus protein (A/PR8/1834 NP). Green, cleaved FlipGFP; blue, nuclei. (C) In black is quantification of the data in panel B. In blue are results of qPCR of CoV 3CLpro or PR8 NP RNA levels relative to untransfected cells. Data are shown as means ± SDs (n = 3); statistical analysis is relative to the NP control. P values were calculated using unpaired, two-tailed Student’s t tests (*, P < 0.05; **, P < 0.001). Experiments were performed twice.