New End Take Off: Regulating Cell Polarity during the Fission

Abstract

Cell polarisation is a major event of the cell cycle and underlies the function of mostcells. Cell polarity is often achieved through the coordinated organisation of themicrotubule and actin cytoskeletons. Dramatic changes in cell polarisation occur duringthe cell cycle and are subject to regulation by cell cycle controls. Cells of the fission yeastSchizosaccharomyces pombe grow by tip extension in a cell cycle-controlled manner.During G2 phase, these cells exhibit a transition in cell polarisation known as New EndTake Off (NETO), in which monopolar cells initiate bipolar growth. Dynamicmicrotubules contribute to this process by depositing at cell ends the microtubule plusend proteins tea1p and tea4p, which are necessary for NETO. We discuss here how theseproteins may recruit for3p, a formin responsible for actin nucleation, as well as two otheractin binding proteins, bud6p and sla2p, to initiate cell polarisation at the new end of thecell. Thus, the study of NETO is revealing a mechanism by which the plus ends ofmicrotubules regulate the spatial organisation of actin.