The focus of the research in my laboratory is the eukaryotic nucleus: its structure and function. We use an in vitro nuclear reconstitution system which efficiently assembles nuclei in the test tube from soluble and membrane components. The system makes use of an extract of Xenopus eggs, which store abundant amounts of disassembled components in preparation for the rapid cleavages of early division. Upon addition of DNA or chromatin to an egg extract, nuclei containing nuclear membranes, a nuclear lamina, and nuclear pores quickly assemble. The in vitro reconstituted nuclei are capable of nuclear import, DNA replication, pol III transcription, and even mitotic disassembly. A major interest of the laboratory is the nuclear pore, a large macromolecular complex of 120 million daltons which spans the nuclear membranes. All communication between the nucleus and cytoplasm occurs through this nuclear pore complex. In vivo the pore actively imports nuclear proteins, while exporting messenger RNA, tRNA, snRNA, and ribosomal precursors. We study: (1) the structure and proteins of the nuclear pore, (2) the mechanism of nuclear transport, and (3) nuclear pore assembly. Using antibodies we can immunodeplete the extract of individual nuclear pore proteins, then reconstitute nuclei which lack that protein. Such "designer" nuclei can be tested for alterations in nuclear pore structure, pore function, or pore assembly. We recently discovered a subunit of the nuclear pore that is a critical determinant of pore assembly (Harel et al, Mol. Cell, 2003). With experiments of this type, we hope to molecularly dissect and elucidate the gates that "guard the fortress" of the genome. A second major interest of the laboratory involves understanding assembly of the eukaryotic nucleus itself. Specifically, we are focused on how nuclear assembly is regulated such that nuclear membranes form around chromatin in a spatially precise manner and, once formed, how the nuclear membranes acquire nuclear pores. Most recently, we have shown that an abundant cellular protein, importin beta, negatively regulates both nuclear membrane fusion and nuclear pore assembly (Harel et al, M.B.C, 2003). We believe that importin beta acts as a global regulator of cellular events involving the genome, controlling nuclear import, spindle formation, correct nuclear membrane assembly, and nuclear pore assembly. Rasala, B.A., Orjalo, A.V., Shen, Z., Briggs, S., and Forbes, D.J. (2006).
ELYS is a dual nucleoporin/kinetochore protein required for nuclear pore assembly and proper cell division. Proceedings of the National Academy of Science 103, 17801-17806. Harel, A., Chan, R. C., Lachish-Zalait, A., Zimmerman, A., Elbaum, M., and Forbes, D. J. (2003). Importin beta negatively regulates nuclear membrane fusion and NPC assembly. Molecular Biology of the Cell, 14: 4387-4396. Vasu, S., Shah, S., Orjalo, A., Park, M., Fischer, W.H., and
Forbes, D.J. (2001). Miller, B.R., and Forbes, D.J. (2000). Purification of the vertebrate nuclear pore by biochemical criteria. Traffic, 1: 941-951. Douglass Forbes received her Ph.D. from the University of Oregon and was a postdoctoral fellow at UCSF in the Dept. of Biochemistry and Biophysics. She was a PEW Fellow in the Biomedical Sciences and on the Governing Council of the American Society of Cell Biology. She is presently Vice Chair of the Section of Cell and Developmental Biology at UCSD. |
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