Fig. 7.

Inactivation of nsp15 endoribonuclease has more impact on viral replication during MERS-CoV infection in Calu3 cells compared to SARS-CoV-2. Calu3 cells were infected with either WT SARS-CoV-2, SARS-CoV-2 nsp15^mut, WT MERS-CoV, MERS-CoV nsp15^mut, or MERS-CoV nsp15^mut/ΔNS4a at MOI 0.1. (A and B) Supernatants were collected at the indicated time points post infection and infectious virus was quantified by plaque assay. (C) Intracellular RNA was extracted at 24 hpi and relative mRNA expression of IFNB and IFNL1 as well as four representative ISGs: RSAD2, IFIT1, CXCL10, and ISG15 was determined by RT-qPCR. Fold change is expressed as 2^−Δ(ΔCt). (D) Western blot analysis of whole cell lysates was performed at indicated time points using antibodies against indicated proteins. Data shown are from one representative experiment of three total experiments.