FIG 5.
M1 suppressor mutations increase virus budding, alter virion protein composition, and enhance infectious virus production. The indicated viruses were used to infect MDCK and MDCK-M2Y76A cells at an MOI of 1.5. Virus particles and infected-cell lysates were collected at 16 hpi. (A) Virus particles partially purified from infected-cell supernatants and the infected-cell lysates were analyzed by Western blotting. Band intensity was quantified using ImageJ and normalized to the intensity of each protein of rUd-M2Stop-infected MDCK cells. Independent experiments were done two to three times, and representative Western blotting data are shown. (B) Viral HA RNA of virus particles was quantified using RT-qPCR with Udorn-HA-specific primers and probes. Relative HA gene in virions was calculated by normalizing the CT value of each sample to that from rUd-M2Stop-infected MDCK cells. (C) Infectious virus titers of virus particles were determined by TCID50 assays (*, P < 0.01; one-way ANOVA with Bonferroni posttest). Data were analyzed from two to three independent experiments. Error bars are standard deviations. Two independent experiments were performed, each in triplicate. The same set of samples was analyzed in all three panels. WT, wild type.