Opening Windows into the Cell: The Molecular Architecture of Nuclear Transport

The nuclear pore complex (NPC) is one of the largest macromolecular machines in the cell, composed of hundreds of proteins, selectively controlling all traffic between the nucleus and the cytoplasm. The architecture of the NPC is central to understanding nuclear transport. However, due to its sheer size, its local environment and its dynamic nature, determining its structure at molecular resolution remains a challenge for conventional techniques. Cryo-electron tomography (cryo-ET) provides unprecedented insights into the 3-D macromolecular organization of cells in their native state, yet the thickness of most cells makes them inaccessible to cryo-ET. I will show how focused ion beam (FIB) milling can be used to prepare 200-500 nm lamellae from intact cells, opening large windows into the cell?s interior, exposing their landscapes at molecular resolution. Combining FIB milling, cryo-ET, and image processing enables the study of the NPC in its native environment, free of the distortions caused by purification. This approach has not only revealed the NPC architecture at unparalleled resolution, but also captured different conformational states in action. I will discuss how the structure obtained by cryo-ET will serve as a scaffold upon which data from a wide range of techniques can be integrated, unveiling the molecular mechanisms of nuclear transport.