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We have found that the mammalian Ran GTPase-activating protein RanGAP1 is highly concentrated at the cytoplasmic periphery of the nuclear pore complex (NPC), where it associates with the 358-kDa Ran-GTP-binding protein RanBP2. This interaction requires the ATP-dependent posttranslational conjugation of RanGAP1 with SUMO-1 (for small ubiquitin-related(More)
To comprehensively identify integral membrane proteins of the nuclear envelope (NE), we prepared separately NEs and organelles known to cofractionate with them from liver. Proteins detected by multidimensional protein identification technology in the cofractionating organelles were subtracted from the NE data set. In addition to all 13 known NE integral(More)
Tpr is a coiled-coil protein found near the nucleoplasmic side of the pore complex. Since neither the precise localization of Tpr nor its functions are well defined, we generated antibodies to three regions of Tpr to clarify these issues. Using light and EM immunolocalization, we determined that mammalian Tpr is concentrated within the nuclear basket of the(More)
Macromolecular trafficking across the nuclear envelope involves interactions between cytosolic transport factors and nuclear pore complex proteins. The p62 complex, an assembly of 62, 58, 54, and 45-kD O-linked glycoproteins-localized near the central gated channel of the nuclear pore complex, has been directly implicated in nuclear protein import. The cDNA(More)
We recently developed an assay in which nuclear export of the shuttling transcription factor NFAT (nuclear factor of activated T cells) can be reconstituted in permeabilized cells with the GTPase Ran and the nuclear export receptor CRM1. We have now used this assay to identify another export factor. After preincubation of permeabilized cells with a Ran(More)
The p62 complex is an oligomeric assembly of O-linked glycoproteins of the nuclear pore complex that interacts with cytosolic transport factors and is part of the machinery for nuclear protein import. In this study we have purified the p62 complex from rat liver nuclear envelopes and analyzed its structure and composition. The p62 complex consists of four(More)
RanBP2, a protein containing FG repeat motifs and four binding sites for the guanosine triphosphatase Ran, is localized at the cytoplasmic periphery of the nuclear pore complex (NPC) and is believed to play a critical role in nuclear protein import. We purified RanBP2 from rat liver nuclear envelopes and examined its structural and biochemical properties.(More)
We have analyzed the fate of several integral membrane proteins of the nuclear envelope during mitosis in cultured mammalian cells to determine whether nuclear membrane proteins are present in a vesicle population distinct from bulk ER membranes after mitotic nuclear envelope disassembly or are dispersed throughout the ER. Using immunofluorescence staining(More)
Lamina-associated polypeptide 2 (LAP2) is an integral membrane protein of the inner nuclear membrane that binds to both lamin B and chromatin and has a putative role in nuclear envelope (NE) organization. We found that microinjection of a recombinant polypeptide comprising the nucleoplasmic domain of rat LAP2 (residues 1-398) into metaphase HeLa cells does(More)
Mediated import of proteins into the nucleus involves multiple cytosolic factors, including the small GTPase Ran. Whether Ran functions by interacting with other cytosolic proteins or components of the nuclear pore complex has been unclear. Furthermore, the precise transport step where Ran acts has not been determined. To address these questions, we have(More)