Movement of a cytokinesis factor cdcl2p to the site of cell division

A key question in cytokinesis is how the plane of cell division is position ed within the cell. Although a number of cytokinesis factors involved in fo rmation of the actomyosin contractile ring have been identified, little is known about how these factors are localized and assembled at the cell-divis ion site. Cells of the fission yeast Schizosaccharomyces pombe divide using a medial actomyosin ring that assembles in early mitosis [1]. The S. pombe cdc12 gene encodes a formin, a member of a family of proteins that have fu nctions in cytokinesis and cell polarity and that may bind Rho/Cdc45 GTPase s, profilin and other actin-associated proteins [1-4]. The cdc12 protein (c dc12p) is required specifically for medial-ring assembly during cytokinesis and is a component of this ring [2,5], In this study, cdc12p was found, du ring interphase, in a discrete, motile cytoplasmic spot that moved to the f uture site of cell division at the onset of mitosis, Three lines of evidenc e indicated that this cdc12p spot moved on both actin and microtubule netwo rks: movement required either actin or microtubules; the spot was associate d with actin and microtubule structures; and individual spots were seen to move along both microtubule and non-microtubule tracks. These findings demo nstrate that a cytokinesis factor may travel on both microtubule and actin networks to the future site of cell division.