Fig 1: Septin suppresses actin tail formation. (A) Immunoblot analysis confirms that SEPT7 siRNA treatment of HeLa cells for 72 h reduces the levels of SEPT7, SEPT2, SEPT9, and SEPT11. (B) Representative immunofluorescence images showing that loss of SEPT7 in uninfected HeLa cells has no obvious impact on the actin cytoskeleton (green). Bar, 50 µm. (C) Immunoblot analysis confirming that infection of HeLa cells with WR vaccinia virus does not alter the level of SEPT2, SEPT7, SEPT9, or SEPT11. (D) Representative images of actin tails (green) induced by WR (red labeled with B5 antibody) in HeLa cells treated with Allstar (control) or SEPT7 siRNA. Bar, 2 µm. The graphs show the quantification of the number of CEVs inducing actin tails and their length. Error bars represent SEM from three independent experiments in which a total of 30 cells were analyzed for actin tail number and 370 tails were measured for length. (E) Quantification of the velocity, directionality, time to form, and duration of actin tails in the absence of SEPT7. Error bars represent SEM from three independent experiments in which a total of >150 actin tails were measured for duration, >50 events for tail initiation from four independent experiments, and >300 actin tails for speed and directionality. *, P < 0.05; **, P < 0.01; ****, P < 0.0001.