Fission yeast Adf1 is necessary for reassembly of actin filaments into the contractile ring during cytokinesis.

ADF/cofilin family proteins quickly disassemble actin in vitro, and are thought to be involved in various actin dynamics in the cell. Adf1 is a member of this family proteins expressed in fission yeast, and is thought to play roles in actin patch dynamics and also contractile ring formation during cytokinesis. We aimed to understand the function of this protein in cytokinesis in detail using the temperature-sensitive mutant adf1-1. Adf1 inactivation at a restrictive temperature during late G2 phase led to a clustering of actin patches at the cell ends. It was apparent that the inactivation occurred only in a few minutes. Furthermore, we found that the actin clusters migrated to the division site during anaphase possibly by the function of both myosin 5-1 and a myosin II. The migrated actin clusters, however, were not organized into the contractile ring. When Adf1 was inactivated at mid-anaphase B before contractile ring assembly, the ring was not formed, but it was formed when Adf1 was inactivated after this point. We conclude that Adf1 functions in the interphase actin dynamics and formation of the contractile ring during mitosis.