Nucleoporin NUP2

UniProtKB accession:  P32499

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UniProtKB description:  Functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. Active directional transport is assured by both, a Phe-Gly (FG) repeat affinity gradient for these transport factors across the NPC and a transport cofactor concentration gradient across the nuclear envelope (GSP1 and GSP2 GTPases associated predominantly with GTP in the nucleus, with GDP in the cytoplasm). As one of the FG repeat nucleoporins NUP2 is involved in interactions with and guidance of nuclear transport receptors such as SRP1-KAP95 (importin alpha and beta) through the NPC. Like the closely related NUP1 it also plays an important role in disassembling and recycling SRP1-KAP95 to the cytoplasm after nuclear import. Upon entry of the heterotrimeric SRP1-KAP95-cargo complex in the nucleus, NUP2 binds through its N-terminus to the SRP1 nuclear localization signal (NLS) binding site, thus accelerating the release of the NLS-cargo. SRP1 in turn is released from NUP2 by binding of the GSP1-GTP associated export factor CSE1. NUP2 may also have a chromatin boundary/insulator activity through indirect interaction with genomic DNA via CSE1 and blocking of heterochromatin spreading.