Nuclear pores dilate and constrict in cellulo

[Figure: see text].

In-cell architecture of the nuclear pore and snapshots of its turnover

Nuclear pore complexes (NPCs) fuse the inner and outer membranes of the nuclear envelope. They comprise hundreds of nucleoporins (Nups) that assemble into multiple subcomplexes and form large central channels for nucleocytoplasmic exchange^1,2. How this architecture facilitates messenger RNA export, NPC biogenesis and turnover remains poorly understood. Here we combine in situ structural biology and integrative modelling with correlative light and electron microscopy and molecular perturbation to structurally analyse NPCs in intact Saccharomyces cerevisiae cells within the context of nuclear envelope remodelling. We find an in situ conformation and configuration of the Nup subcomplexes that was unexpected from the results of previous in vitro analyses. The configuration of the Nup159 complex appears critical to spatially accommodate its function as an mRNA export platform, and as a mediator of NPC turnover. The omega-shaped nuclear envelope herniae that accumulate in nup116Δ cells³ conceal partially assembled NPCs lacking multiple subcomplexes, including the Nup159 complex. Under conditions of starvation, herniae of a second type are formed that cytoplasmically expose NPCs. These results point to a model of NPC turnover in which NPC-containing vesicles bud off from the nuclear envelope before degradation by the autophagy machinery. Our study emphasizes the importance of investigating the structure-function relationship of macromolecular complexes in their cellular context.

TCRpMHCmodels: Structural modelling of TCR-pMHC class I complexes

The interaction between the class I major histocompatibility complex (MHC), the peptide presented by the MHC and the T-cell receptor (TCR) is a key determinant of the cellular immune response. Here, we present TCRpMHCmodels, a method for accurate structural modelling of the TCR-peptide-MHC (TCR-pMHC) complex. This TCR-pMHC modelling pipeline takes as input the amino acid sequence and generates models of the TCR-pMHC complex, with a median Cα RMSD of 2.31 Å. TCRpMHCmodels significantly outperforms TCRFlexDock, a specialised method for docking pMHC and TCR structures. TCRpMHCmodels is simple to use and the modelling pipeline takes, on average, only two minutes. Thanks to its ease of use and high modelling accuracy, we expect TCRpMHCmodels to provide insights into the underlying mechanisms of TCR and pMHC interactions and aid in the development of advanced T-cell-based immunotherapies and rational design of vaccines. The TCRpMHCmodels tool is available at http://www.cbs.dtu.dk/services/TCRpMHCmodels/.