The actin cytoskeleton is a highly dynamic network composed of actin polyme
rs and a large variety of associated proteins. The main functions of the ac
tin cytoskeleton are to mediate cell motility and cell shape changes during
the cell cycle and in response to extracellular stimuli, to organize the c
ytoplasm, and to generate mechanical forces within the cell. The reshaping
and functions of the actin cytoskeleton are regulated by signaling pathways
. Here we broadly review the actin cytoskeleton and the signaling pathways
that regulate it. We place heavy emphasis on the yeast actin cytoskeleton.