Recruitment of the mitotic exit network to yeast centrosomes couples septin displacement to actomyosin constriction

Davide Tamborrini,Sandy Ibanes,Giulia Rancati,Maria Angeles Juanes,Simonetta Piatti

doi:10.1038/s41467-018-06767-0

Abstract

In many eukaryotic organisms cytokinesis is driven by a contractile actomyosin ring (CAR) that guides membrane invagination. What triggers CAR constriction at a precise time of the cell cycle is a fundamental question. In budding yeast CAR is assembled via a septin scaffold at the division site. A Hippo-like kinase cascade, the Mitotic Exit Network (MEN), promotes mitotic exit and cytokinesis, but whether and how these two processes are independently controlled by MEN is poorly understood. Here we show that a critical function of MEN is to promote displacement of the septin ring from the division site, which in turn is essential for CAR constriction. This is independent of MEN control over mitotic exit and involves recruitment of MEN components to the spindle pole body (SPB). Ubiquitination of the SPB scaffold Nud1 inhibits MEN signaling at the end of mitosis and prevents septin ring splitting, thus silencing the cytokinetic machinery.

Highlights

In many eukaryotic organisms cytokinesis is driven by a contractile actomyosin ring (CAR) that guides membrane invagination
Taking advantage of yeast strains that are defective in septin ring splitting, we demonstrate that septin ring splitting/ displacement is an essential prerequisite for CAR contraction and for cytokinesis
Previous data showed that CAR constriction occurs approximately at the same time as septin ring splitting[7,8]

Summary

Introduction

In many eukaryotic organisms cytokinesis is driven by a contractile actomyosin ring (CAR) that guides membrane invagination. We show that a critical function of MEN is to promote displacement of the septin ring from the division site, which in turn is essential for CAR constriction This is independent of MEN control over mitotic exit and involves recruitment of MEN components to the spindle pole body (SPB). Studies in budding yeast and mammalian cells indicate that septins act as scaffolds to recruit cytokinesis factors to the site of cell division and regulate CAR constriction In fission yeast a Hippo-like signaling cascade, called septation initiation network (SIN), has exactly the same organization of MEN and is essential for cytokinesis without being involved in mitotic exit In fission yeast a Hippo-like signaling cascade, called septation initiation network (SIN), has exactly the same organization of MEN and is essential for cytokinesis without being involved in mitotic exit (reviewed in ref. 21)

Methods

Results

Conclusion