Proteins and nucleic acids are transported between the cytoplasm and nucleus through nuclear pores, huge disc-shaped macromolecular assemblies about 125nm in diameter that perforate the nuclear envelope. Cargo macromolecules are transported through the pores by specific carrier molecules and this process is often orchestrated by the Ran GTPase. The long-term goal of my group is to understand the nuclear transport machinery at the molecular level. To do this, a combination of structural, molecular and cellular methods is being used to establish the structure of the proteins involved and how they interact with one another to generate transport.
Thus, the structures of a range of transport factors together with their complexes with nuclear pore proteins (nucleoporins), cargoes and Ran have been established by crystallography or NMR. This structural information has then been used to engineer specific mutants that have been used to define the role of each interaction in the overall process.
Future work will concentrate on two main areas. The first is to address the molecular mechanism of the nuclear export of mRNA, concentrating on the assembly of export-competent mRNPs in the nucleus and their disassembly in the cytoplasm.
The second area we are concentrating on is to investigate the role of nuclear trafficking components, the TREX-2 complex, and the polyA-binding protein, Nab2p, in orchestrating the gene expression machinery, especially in the context of their acting as scaffolds for the formation of the large macromolecular complexes involved in transcription, splicing, mRNA processing and nuclear export.
In each case, we will aim to use X-ray crystallography, NMR and EM to obtain the structure of the components and their interaction interfaces, and then use this information to generate mutants that can address the functional importance of these interactions.
- Ellisdon, A.M., Dimitrova, L., Hurt, E. and Stewart, M. (2012)
Structural basis for the assembly and nucleic acid binding of the TREX-2 transcription-export complex.
Nature Struct Mol Biol 19: 328-336.
- Jani, D., Lutz, S., Marshall, N.J., Fischer, T., Köhler, A., Ellisdon, A.M., Hurt, E. and Stewart, M. (2009)
Sus1, Cdc31, and the Sac3 CID region form a conserved interaction platform that promotes nuclear pore association and mRNA export.
Molecular Cell 33: 727-737.
- Lee, S.J., Matsuura, Y., Liu, S.M. and Stewart, M. (2005)
Structural basis for nuclear import complex disassembly by RanGTP.
Nature 435: 693-696.
- Matsuura, Y. and Stewart, M. (2004)
Structural basis for the assembly of a nuclear export complex.
Nature 432: 872-877.