http://www.ncbi.nlm.nih.gov – Nuclear pore complexes (NPCs) control the traffic between cell nucleus and cytoplasm. While facilitating translocation of nuclear transport receptors (NTRs) and NTR·cargo complexes, they suppress passive passage of macromolecules 30 kDa. Previously, we reconstituted the NPC barrier as hydrogels comprising S. cerevisiae FG domains. We now studied FG domains from 10 Xenopus nucleoporins and found that all of them form hydrogels. Related domains with low FG motif density also substantially contribute to the NPC's hydrogel mass. Read more »

http://www.ncbi.nlm.nih.gov – Key steps in mRNA export are the nuclear assembly of messenger ribonucleoprotein particles (mRNPs), the translocation of mRNPs through the nuclear pore complex (NPC), and the mRNP remodeling events at the cytoplasmic side of the NPC. Nup358/RanBP2 is a constituent of the cytoplasmic filaments of the NPC specific to higher eukaryotes and provides a multitude of binding sites for the nucleocytoplasmic transport machinery. Here, we present the crystal structure of the Nup358 N-terminal domain (NTD) at 0.95-Å resolution. Read more »

http://www.ncbi.nlm.nih.gov – The nuclear pore complex (NPC) mediates macromolecular exchange between nucleus and cytoplasm. It is a regulated channel whose functional properties are modulated in response to the physiological status of the cell. Identifying the factors responsible for regulating NPC activity is crucial to understand how intracellular signaling cues are integrated at the level of this channel to control nucleocytoplasmic trafficking. For proteins lacking active translocation signals the NPC acts as a molecular sieve limiting passage across the nuclear envelope (NE) to proteins with a MW below ~40 kD. Read more »

http://www.ncbi.nlm.nih.gov – XAB1/Gpn1 is a GTPase that associates with RNA polymerase II (RNAPII) in a GTP-dependent manner. Although XAB1/Gpn1 is essential for nuclear accumulation of RNAPII, the underlying mechanism is not known. A XAB1/Gpn1-EYFP fluorescent protein, like endogenous XAB1/Gpn1, localized to the cytoplasm but it rapidly accumulated in the cell nucleus in the presence of leptomycin B, a chemical inhibitor of the nuclear transport receptor Crm1. Crm1 recognizes short peptides in substrate proteins called nuclear export sequences (NES). Read more »

http://www.ncbi.nlm.nih.gov – The eukaryotic translation initiation factor eIF4E is a potent oncogene that promotes the nuclear export and translation of specific transcripts. Here, we have discovered that eIF4E alters the cytoplasmic face of the nuclear pore complex (NPC), which leads to enhanced mRNA export of eIF4E target mRNAs. Specifically, eIF4E substantially reduces the major component of the cytoplasmic fibrils of the NPC, RanBP2, relocalizes an associated nucleoporin, Nup214, and elevates RanBP1 and the RNA export factors, Gle1 and DDX19. Genetic or pharmacological inhibition of eIF4E impedes these effects. Read more »