Bmf (for Bcl-2-modifying factor) is a novel BH3-only protein recently identified in human and mouse. The BH3 domain in Bmf is required for both binding to Bcl-2 proteins and for triggering apoptosis. In healthy cells, Bmf associates with the dynein light chain 2 (DLC2) component of the myosin V motors and is sequestered by the cell's actin cytoskeleton. Disruption of the actin cytoskeleton, either by depolymerization of actin filaments or by detachment of cells from the extracellular matrix, triggers release and activation of Bmf, initiating the downstream apoptosis program.