Fig. 1

Preferential M2 splicing in H1N1 over H3N2 influenza viruses. a Diagram of M segment splicing. The primers used are depicted (colored arrows). b, c Splicing pattern of M in HEK293 cells infected by six IAV strains (MOI = 1): A/WSN/33 (WSN), A/Puerto Rico/8/34 (PR8), A/TW/3773/2015 (pH1N1), A/Udorn/1972 (Udorn), A/TW/3446/2002 (3446), and A/TW/2032/2017 (2032). Total RNA was collected 5 and 8 h post-infection (hpi) and the splicing products were detected using RT-PCR (b) and qPCR (c). Fold change compared with WSN is expressed as the ratio of M2 to all M mRNA. d HEK293 and DF-1 cells were infected with WSN, pH1N1, and 2032 (MOI = 1), and total RNA was collected at 5 hpi. e HEK293 cells were co-transfected with expressing plasmids encoding RNP (PB2, PB1, PA, and NP) and M reporter plasmids from different strains as indicated. After 48 h, total RNA was collected and analyzed. Densitometric analysis of each mRNA was quantified using ImageJ