THE SCHIZOSACCHAROMYCES-POMBE ACTIN-RELATED PROTEIN, ARP3, IS A COMPONENT OF THE CORTICAL ACTIN CYTOSKELETON AND INTERACTS WITH PROFILIN

The gene encoding the actin-related protein Arp3 was first identified in the fission yeast Schizosaccharomyces pombe and is a member of an e volutionarily conserved family of actin-related proteins. Here we pres ent several key findings that define an essential role for Arp3p in th e functioning of the cortical actin cytoskeleton. First, mutants in ar p3 interact specifically with profilin and actin mutants, Second, Arp3 localizes to cortical actin patches which are required for polarized cell growth. Third, the arp3 gene is required for the reorganization o f the actin cytoskeleton during the cell cycle, Finally, the Arp3 prot ein is present in a large protein complex. We believe that this comple x may mediate the cortical functions of profilin at actin patches in S . pombe.