Loss of a nucleoporin disrupts kinetochore structure (brackets).
The first of the mystery proteins is the nucleoporin Nup358, a component of the filaments on the cytoplasmic face of the nuclear envelope. On page 991, Salina et al. show that loss of Nup358 does not block nuclear import but does impair mitosis. During division, cells lacking Nup358 formed abnormal spindles and stalled in metaphase.
Several nuclear pore complex proteins associate with kinetochores in dividing cells, including Nup358. Indeed, the division problems stemmed from abnormal kinetochores. Without Nup358, kinetochore morphology was perturbed, and kinetochore proteins such as dynein, CENP-E, and Mad2 were mislocalized. That the mitotic checkpoint was activated in these cells bolsters the recent argument that checkpoint proteins can signal from the cytoplasm.
The...
