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A more recent version of this article appeared on February 1, 2006
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Submitted on June 3, 2005
Revised on November 4, 2005
Accepted on November 16, 2005

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*Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112;
Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
Monitoring Editor: Susan Wente
When higher eukaryotic cells transition into mitosis, the nuclear envelope, nuclear pore complexes, and nuclear lamina are coordinately disassembled. The COPI coatomer complex, which plays a major role in membrane remodeling at the Golgi, has been implicated in the process of nuclear envelope breakdown and requires interactions at the nuclear pore complex for recruitment to this new site of action at mitosis. Nup153, a resident of the nuclear pore basket, was found to be involved in COPI recruitment, but the molecular nature of the interface between COPI and the nuclear pore has not been fully elucidated. To better understand what occurs at the nuclear pore at this juncture, we have probed the role of the nucleoporin Nup358/RanBP2. Nup358 contains a repetitive zinc finger domain with overall organization similar to a region within Nup153 that is critical to COPI association, yet inspection of these two zinc finger domains reveals features which also clearly distinguish them. Here, we found that the Nup358 zinc finger domain, but not a zinc finger domain from an unrelated protein, binds to COPI and dominantly inhibits progression of nuclear envelope breakdown in an assay that robustly recapitulates this process in vitro. Moreover, the Nup358 zinc finger domain interferes with COPI recruitment to the nuclear rim. Consistent with a role for this pore protein in coordinating nuclear envelope breakdown, Nup358-specific antibodies impair nuclear disassembly. Significantly, targeting either Nup153 or Nup358 for inhibition perturbs nuclear envelope breakdown, supporting a model in which these nucleoporins play nonredundant roles, perhaps contributing to COPI recruitment platforms on both the nuclear and cytoplasmic faces of the pore. We found that an individual zinc finger is the minimal interface for COPI association, although tandem zinc fingers are optimal. These results provide new information about the critical components of nuclear membrane remodeling and lay the foundation for a better understanding of how this process is regulated.
These authors contributed equally to this work.
Present addresses:
Section of Molecular and Cellular Biology and Center for Genetics and Development, University of California, Davis, CA 95616; ||National Center for Cell Science, Ganeshkhind, Pune 411007, India.
Address correspondence to:
Katharine S. Ullman (Katharine.ullman{at}hci.utah.edu)
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