Actin-based motility processes are tightly-linked to the rapid turnove
r of actin filaments. Factors that control the steady state of actin a
ssembly, such as capping proteins and actin-depolymerizing factor/cofi
lin, directly affect motility. Actin-depolymerizing factor increases t
he treadmilling of actin filaments in vitro and in vivo. Cellular fact
ors that are involved in linking initiation of barbed end assembly to
cell signaling are being identified using Listeria monocytogenes and S
accharomyces cerevisiae as model systems.