FIG 4.

M1 suppressor mutations also induce filamentous virus budding in the absence of M2. (A) MDCK, MDCK-M2Y76A, and MDCK-M2 cells were infected at a high MOI with rUd-M2Stop, rUd-M1G73R/M2Stop, and rUd-M1V138M/M2Stop. Filamentous particle budding at 16 hpi was analyzed by immunofluorescence assay. HA, NS1, and nucleus are shown in green, red, and blue, respectively. The images were taken with an LSM 510 confocal microscope with a 100× objective. Independent experiments were done three times, and representative images are shown. (B to D) The percentages of infected cells showing viral filaments per field of rUd-M2Stop (B), rUd-M1G73R/M2Stop (C), and rUd-M1V138M/M2Stop (D) viruses were quantified by counting 20 fields per sample (*, P < 0.01; one-way ANOVA with Bonferroni posttest compared to MDCK-M2 cells). The data shown are from one of three independent experiments, all of which had similar results.