The keratin cycle. Soluble keratin oligomers assemble into particles in the cell periphery in proximity to focal adhesion sites (nucleation). These particles grow (elongation) and move toward the cell center in an actin-dependent process (transport). Subsequently, elongated KF particles are incorporated into the peripheral KF network (integration). Filament bundling occurs during further centripetal translocation toward the nucleus (transport). Soluble oligomers dissociate (disassembly), diffuse throughout the cytoplasm (diffusion), and are reutilized for another cycle of KF formation in the cell periphery. Alternatively, bundled filaments are stabilized (maturation), forming, e.g., the stable perinuclear cage.