Repairing tears in the nuclear envelope The nuclear envelope segregates genomic DNA from the cytoplasm and regulates protein trafficking between the cytosol and the nucleus. Maintaining nuclear envelope integrity during interphase is considered crucial. However, Raab et al. and Denais et al. show that migrating immune and cancer cells experience frequent and transitory nuclear envelope ruptures when they move through tight spaces (see the Perspective by Burke). The nuclear envelope reseals rapidly during interphase, assisted by components of the ESCRT III membrane-remodeling machinery. Science , this issue pp. 359 and 353 ; see also p. 295