eLife assessment
The intrinsic chirality of actin filaments (F-actin) is implicated in the chiral arrangement and movement of cellular structures, but it was unknown how opposite chiralities can arise when the chirality of F-actin is invariant. Kwong et al. present evidence that two actin filament-based cytoskeletal structures, transverse actin arcs and radial stress fibers, drive clockwise and anti-clockwise rotation, respectively. This fundamental work, which has broad implications for cell biology, is supported by compelling data.