Our goal is to understand the mechanism for highly selective, bidirectional exchange of proteins and RNA between the nucleus and cytoplasm. Nucleocytoplasmic trafficking is essential for cell function, and precisely regulated during cell division, differentiation and death. Many aspects of this process are poorly understood. At the center of the transport mechanism are the nuclear pore complexes (NPCs), large protein machines embedded in the nuclear envelope and the only known sites for nuclear entry and exit. We use yeast, cultured human cells, and zebrafish model systems to address three broad questions.
(1) How are NPCs assembled? At least 30 different proteins associate in a nuclear envelope pore to form an NPC. Using genetic strategies and GFP-tagged NPCs, we are identifying assembly factors and monitoring NPC dynamics in live cells.
(2) How do proteins and genetic material move through the NPC? By genetic, molecular and biochemical means, we are investigating the mechanism by which transport factors utilize NPC proteins for movement. Studies also focus on elucidating steps in mRNA export, coupling between mRNA export and translation, and roles for inositol polyphosphate signaling in regulating transport.
(3) How do inositol signaling and mRNA export molecules regulate vertebrate development and disease? Using the zebrafish model system, we have made multiple discoveries that open up entirely new areas of investigation.
These basic projects impact human disease in several ways. Proper NPC assembly is required for maintaining transport in rapidly dividing cells (e.g. cancer cells), and for cell division in higher eukaryotes. Cancer cells can also alter gene expression by perturbing nuclear transport. Furthermore, transport factors and NPC proteins are targets for viral inhibition of cell function and mediators of viral RNA export. We predict that analyzing NPC translocation and assembly mechanisms will identify targets for controlling cancer cell growth or viral pathogenesis. Of note, an essential mRNA export factor discovered in our laboratory is linked to a severe form of human motor neuron degeneration, and we are specifically investing effort to reveal this disease mechanism. Overall, our future work will continue to integrate our discoveries from the analysis of single cell machineries into the context of multicellular organism development and pathophysiology.