Repression of PSMB8-AS1 reduces influenza virus replication. A549 cells stably expressed dCas9-KRAB were infected with lentiviral gRNAs at a MOI of 200 in the presence of 0.1 µg/ml of puromycin for 48 h and infected with PR/8 at a MOI of 0.01 for 48 h. (A) PSMB8-AS1 expression level and (B) NP and NS1 mRNA levels as determined by real-time PCR. (C, D) NP, NS1 and PB1 protein levels as determined by western blotting. The protein bands were quantitated using Image Quant software and normalized to β-actin. (E, F) % NP-positive cells as revealed by immunostaining. (G)Virus titer in medium as determined by a plaque assay. (H) Cell viability as determined by a Cell-Titer Blue assay (Promega G8080). *P < 0.05, **p < 0.01, ***p < 0.001 (n = 3, one-way ANOVA, Tukey’s).