Faleiro et al. (page 951) report that caspases can disrupt the nuclear-cytoplasmic barrier by increasing the diffusion limit of nuclear pores, promoting the disassembly of the cell, and allowing caspases to enter the nucleus during apoptosis. The results help explain how caspases, which are ordinarily located in the cytoplasm, can reach molecular targets within the nucleus to carry out apoptosis.
Although the caspase-mediated signaling pathways that carry out apoptosis have been studied extensively, the mechanisms governing transport of caspases into the nucleus have remained poorly understood. By examining the localization of GFP-tagged caspase-3, the authors determined that the protein enters the nucleus during apoptosis, and that the activity of caspase-9 is required for this translocation. Caspase-9 activity also allows other large proteins to enter the nucleus, apparently by increasing the diffusion limit of nuclear pores. The findings point to...
