USP1 and influenza: After infecting the sh-control, sh-usp1, and WT cells with four subtypes of influenza strains (H1 N1, H3 N2, BY, BV) at MOI = 0.01, samples of the supernatants were collected at 12 h, 24 h, 36 h, 48 h, and 60 h post-infection for the TCID50 assay.