Nup2 requires a highly divergent partner, NupA, to fulfill functions at nuclear pore complexes and the mitotic chromatin region.
Bottom Line: These mitotic problems are not caused by overall defects in mitotic NPC disassembly-reassembly or general nuclear import.However, without Nup2 or NupA, although the SAC protein Mad1 locates to its mitotic locations, it fails to locate to NPCs normally in G1 after mitosis.Collectively the study provides new insight into the roles of Nup2 and NupA during mitosis and in a surveillance mechanism that regulates nucleokinesis when mitotic defects occur after SAC fulfillment.
Affiliation: Laboratory of Gene Regulation and Development, National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.Show MeSH
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Mentions: A. nidulans NPCs undergo partial disassembly during mitosis, and the NIMA kinase is able to promote NPC disassembly when ectopically expressed, even during interphase (De Souza et al., 2004; De Souza and Osmani, 2007). We therefore sought to determine whether NIMA could promote the removal of Nup2 from NPCs and perhaps even trigger its transition to the chromatin region. We used a strain able to express a stable kinase-active, C-terminally truncated (NIMAΔC) version of NIMA (Pu and Osmani, 1995) under control of the regulatable alcA promoter (Waring et al., 1989). The expression of NIMAΔC was turned on in untreated cells or cells arrested in S phase by hydroxyurea (HU). The abundance of NIMAΔC and subsequent mobility shifts for endogenous NIMA and Nup2 were monitored via Western blot analysis (Figure 2A). An increase in the level of NIMAΔC occurred after 30 min of induction and accumulated further with time of induction. The increase in NIMAΔC levels correlated with mobility shifts in endogenous NIMA and Nup2, indicating that extra NIMAΔC promotes the phosphorylation of both. A similar pattern was seen after induction of NIMAΔC in the presence of HU, but in this case, induction of NIMAΔC was delayed, as were the mobility shifts of endogenous NIMA and Nup2 (Figure 2A, right).
Affiliation: Laboratory of Gene Regulation and Development, National Institute for Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.