Fig. 1: SARS-CoV-2 RNA but not SARS-CoV-2 infection induces SG formation.

a Induction of SGs by arsenite, transfection of poly(I:C) and SARS-CoV-2 RNA. HeLa cells were treated with sodium arsenite (1 mM) for 1 h or transfected with poly(I:C) (2 μg) or SARS-CoV-2 RNA (1 μg) for 10 h. Cells were immunostained for TIA-1 (green) and G3BP1 (red). Nuclei were stained with DAPI (blue). The cells were observed with a Nikon confocal microscope under a 60× oil objective. b SGs were not induced by SARS-CoV-2 infection. HeLa-ACE2 cells were infected with SARS-CoV-2 (MOI = 1) for indicated times, and then untreated or treated with sodium arsenite (1 mM) for 1 h. Cells were immunostained for TIA-1 (green) and G3BP1 (red). Nuclei were stained with DAPI (blue). The cells were observed with a Nikon confocal microscope under a 60× oil objective. c Transfection of poly(I:C) and SARS-CoV-2 RNA and arsenite treatment induced PKR and eIF2α phosphorylation. HeLa cells were treated with sodium arsenite (1 mM) for 1 h or transfected with poly(I:C) (3 μg) or SARS-CoV-2 RNA (2 μg) for 10 h before immunoblot analysis with the indicated antibodies. d SARS-CoV-2 infection did not induce PKR and eIF2α phosphorylation. HeLa-ACE2 cells were infected with SARS-CoV-2 (MOI = 1) for indicated times and then untreated or treated with sodium arsenite (1 mM) for 1 h before immunoblot analysis with the indicated antibodies. e–g Formation of SGs induced by RNAs requires PKR and G3BP1. PKR and G3BP1 in HeLa cells were knocked out with the CRISPR/Cas9 system. The knockout efficiencies were detected by immunoblot with the indicated antibodies (e). PKR- (gPKR) (f), G3BP1- (gG3BP1) (g), and control-knockout (gNC) HeLa cells were treated with sodium arsenite (1 mM) for 1 h or transfected with poly(I:C) (2 μg) or SARS-CoV-2 RNA (1 μg) for 10 h. The cells were then immunostained for TIA-1 (green) and G3BP1(red) or G3BP2 (red). Nuclei were stained with DAPI (blue). The cells were observed with a Nikon confocal microscope under a 60× oil objective.