The nuclear envelope (NE) is constantly having to remodel itself – before cell division the envelope breaks down and at the end of cell division it is reformed. Hemmo Meyer and colleagues are interested in the way that reformation of the NE by membrane fusion is mediated and coordinated with assembly of nuclear pore complexes (NPCs) – the complexes that allow molecules to move in and out of the nucleus. On , they turn their attention to crucial mediators of membrane fusion: the SNAREs (interacting membrane proteins present on the two membranes that fuse) and NSF (a protein that dissociates the SNARE complex after membrane fusion). Analysing extracts of Xenopus eggs by fluorescence microscopy, they find that, without NSF, reformation of the NE membrane cannot occur. Blocking SNARE function causes a similar fusion defect, and, although certain NPC proteins are recruited, without NSF and SNAREs these `nucleoporins' do not assemble into NPCs. Looking more closely at the timing of events, the researchers see that NSF is required right up until the chromatin is completely surrounded by the NE. They go on to discuss the possibility that NSF works closely with the ATPase p97, a protein also required at late stages of NE formation.
