FIG 1.

DDX21 restricts SARS-CoV-2 infection. (A) Inhibition of host cellular RNA helicase protein expression by the shRNA-producing lentiviral vector. The results of Western blot analysis of cellular lysates with anti-DDX1 (A300-521A), anti-DDX3 (A300-474A), anti-DDX6 (A300-460A), anti-DDX21 (A300-627A), anti-MOV10 (A301-571A), or anti-β-actin antibody are shown. (B) The level of intracellular SARS-CoV-2 RNA in the cells at 72 h postinfection at an MOI of 0.5 was monitored by real-time LightCycler RT-PCR. Results from three independent experiments are shown. The level of SARS-CoV-2 RNA in knockdown cells was calculated relative to the level in HEK293T ACE2 cells transduced with a control lentiviral vector (Con). *, P < 0.05 compared to control cells. Cq, quantitation cycle. (C) SARS-CoV-2 spike protein expression levels in knockdown cells. The results of the Western blot analysis of cellular lysates with anti-SARS-CoV-2 Spike (GTX632604 [1A9]) or anti-β-actin antibody in the SARS-CoV-2-infected HEK293T ACE2 cells at 72 h postinfection at an MOI of 0.5 are shown. (D) DDX21 restricts SARS-CoV-2 infection in Caco-2 and HepG2 cells. Inhibition of endogenous DDX21 protein expression by the shRNA-producing lentiviral vector. The results of Western blot analysis of cellular lysates with anti-DDX21 or anti-β-actin antibody in Caco-2 and HepG2 cells are shown. The level of intracellular SARS-CoV-2 RNA in the cells at 72 h postinfection at an MOI of 0.5 was monitored by real-time LightCycler RT-PCR. Results from three independent experiments are shown. The level of SARS-CoV-2 RNA in DDX21 knockdown cells was calculated relative to the level in HEK293T ACE2 cells transduced with a control lentiviral vector (Con). *, P < 0.05 compared to control cells.