ESCRT-III controls nuclear envelope reformation

During telophase, the nuclear envelope (NE) reforms around daughter nuclei to ensure proper segregation of nuclear and cytoplasmic contents(1-4). NE reformation requires the coating of chromatin by membrane derived from the Endoplasmic Reticulum and a subsequent annular fusion step to ensure the formed envelope is sealed(1,2,4,5). How annular fusion is accomplished is unknown, but it is thought to involve the p97 AAA-ATPase complex and bears a topological equivalence to the membrane fusion event that occurs during the abscission phase of cytokinesis(1,6). We find here that the Endosomal Sorting Complex Required for Transport-III (ESCRT-III) machinery localises to sites of annular fusion in the forming NE and is necessary for proper post-mitotic nucleo-cytoplasmic compartmentalisation. The ESCRT-III component Charged Multivesicular Body Protein (CHMP) 2A is directed to the forming NE through binding to CHMP4B and provides an activity essential for NE reformation. Localisation also requires the p97 complex member Ubiquitin Fusion and Degradation 1 (UFD1). Our results describe a novel role for the ESCRT-machinery in cell division and demonstrate a conservation of the machineries involved in topologically equivalent mitotic membrane remodeling events.