I did my Ph.D. work in the laboratory of Mike Rout at The Rockefeller University. I worked on a basic cell biology and biochemistry question: What is the role of Mlp1 and Mlp2 in yeast? I initially pursued a phenotypic approach, but the array of phenotypes by deletion of Mlp proteins proved to be too confusing to interpret. Instead, I optimized a biochemical approach to isolate native complexes from yeast and analyze the components by mass spec.
In agreement with previous findings, the dominant binding partners of Mlps were components of the NPC and the mRNA processing and transport machinery. However, I also identified a large number of spindle pole body components in contact with Mlp2. I characterized this interaction in more detail and identified to role Mlp2 plays in spindle body assembly and maintenance. This work was published in The Journal of Cell Biology.
In a second publication I further explored the structural role played by Mlp1 and Mlp2 at the nuclear envelope. Both proteins together form the basket the nuclear pore complex which is likely where they exert their influence on mRNA quality control and export. In addition, the Mlps bind each other and form a protein network that spans much of the nuclear envelope. This protein network physically stabilizes the nucleus and it also serves as an assembly platform of complexes at the envelope, including Esc1p and the proteasome.
My colleagues and I got a great opportunity to summarize much of what we learned in the past decade about the role of the NPC and its peripherally associated structures for nuclear function in a review for Nature Reviews Molecular Cell Biology. In it we laid out how the nuclear pore complex is emerging as an important regulator of gene expression. Both, through its influence on the organization of the nucleus and through its apparently extensive involvement in coordinating the delivery of mRNA to the cytoplasmic protein synthesis machinery.
Niepel, Mario, Caterina Strambio-De-Castillia, Joseph Fasolo, Brian T Chait, and Michael P Rout. “The nuclear pore complex-associated protein, Mlp2p, binds to the yeast spindle pole body and promotes its efficient assembly.” The Journal of cell biology 170, no. 2 (2005): 225 - 35.
Strambio-De-Castillia, Caterina, Mario Niepel, and Michael P Rout. “The nuclear pore complex: bridging nuclear transport and gene regulation.” Nature Reviews Molecular Cell Biology 11, no. 7 (2010): 490 - 501.
Niepel, Mario, Kelly R Molloy, Rosemary Williams, Julia C Farr, Anne C Meinema, Nicholas Vecchietti, Ileana M Cristea, Brian T Chait, Michael P Rout, and Caterina Strambio-De-Castillia. “The nuclear basket proteins Mlp1p and Mlp2p are part of a dynamic interactome including Esc1p and the proteasome.” Molecular biology of the cell 24, no. 24 (2013): 3920 - 3938.
Niepel, Mario, Julia C Farr, Rosemary Williams, Anne C Meinema, Michael P Rout, and Caterina Strambio-De-Castillia. “Rapid isolation of functionally intact nuclei from the yeast Saccharomyces” Molecular biology of the cell (under review)