Biology subjects

Antonin, W.

Publications and source records attributed to Antonin, W..

3 recordsLinked to original sources

bioRxiv2022

New motifs in Ndc1 mediating interaction with the Nup84 complex and nuclear membranes

The nuclear pore complex (NPC) embedded in the double nuclear membrane is built from ~30 different nucleoporins (Nups) in multiple copies, of which a few are integral nuclear membrane proteins. One of these transmembrane Nups is Ndc1, which is thought to play a role in interphase NPC assembly at the fused inner and outer nuclear membrane. In this study, we discovered a direct interaction of Ndc1s transmembrane domain with Nup120 and Nup133, members of the Y-complex that coats the nuclear pore membrane. In addition, we identified a so far unrecognized amphipathic helix (AH) in the C-terminal domain of Ndc1, which can bind to high curvature liposomes. When overexpressed in yeast this amphipathic motif is toxic and dramatically alters the intracellular membrane organization. Further genetic investigations revealed that Ndc1-AH functionally interacts with related motifs in the C-terminus of Nups Nup53 and Nup59, known to serve in nuclear pore membrane binding and link between NPC modules. This relationship could explain why the essential function of Ndc1 can be suppressed by deleting the amphipathic helix from Nup53. Our data indicate that nuclear membrane biogenesis dependent on a balanced ratio between amphipathic motifs in diverse nucleoporins is essential for interphase NPC biogenesis.

cell biology↗

bioRxiv2022

An amphipathic helix in Brl1 is required for membrane fusion during nuclear pore complex biogenesis in S. cerevisiae

The nuclear pore complex (NPC) is the central portal for macromolecular exchange between the nucleus and cytoplasm. In all eukaryotes, NPCs assemble into an intact nuclear envelope (NE) during interphase, but the process of NPC biogenesis remains poorly characterized. Furthermore, little is known about how NPC assembly leads to the fusion of the outer and inner NE, and no factors have been identified that could trigger this event. Here we characterize the transmembrane protein Brl1 as an NPC assembly factor required for NE fusion in budding yeast. Brl1 preferentially associates with NPC assembly intermediates and its depletion halts NPC biogenesis, leading to NE herniations that contain inner and outer ring nucleoporins but lack the cytoplasmic export platform. Furthermore, we identify an essential amphipathic helix in the luminal domain of Brl1 that mediates interactions with lipid bilayers. Mutations in this amphipathic helix lead to NPC assembly defects, and cryo-ET analyses reveal multi-layered herniations of the inner nuclear membrane with NPC-like structures at the neck, indicating a failure in NE fusion. Taken together, our results identify a role for Brl1 in NPC assembly and suggest a function of its amphipathic helix in mediating the fusion of the inner and outer nuclear membranes.

cell biology↗

bioRxiv2021

The nucleoporin Nup50 activates the Ran guanyl-nucleotide exchange factor RCC1 to promote mitotic NPC assembly

During mitotic exit, thousands of nuclear pore complexes (NPCs) assemble concomitant with the nuclear envelope to build a transport-competent nucleus. We show here that Nup50 plays a crucial role in NPC assembly that is independent of its well-established function in nuclear transport. RNAi-mediated downregulation in cells or immunodepletion of the protein in Xenopus egg extracts interferes with NPC assembly. We define a conserved central region of 46 residues in Nup50 that is crucial for Nup153 and MEL28/ELYS binding, and NPC interaction. Surprisingly, neither NPC interaction nor binding of Nup50 to importin , {beta}, the GTPase Ran or chromatin is crucial for its function in the assembly process. Instead, we discovered that an N-terminal fragment of Nup50 can stimulate the Ran guanine exchange factor RCC1 and NPC assembly, indicating that Nup50 acts via the Ran system in mitotic NPC reformation. In support of this conclusion, Nup50 mutants defective in RCC1 binding and stimulation cannot replace the wild type protein in in vitro NPC assembly assays.

cell biology↗