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EMBO J 2021 Dec 01;4023:e108788. doi: 10.15252/embj.2021108788.
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The nucleoporin Nup50 activates the Ran guanine nucleotide exchange factor RCC1 to promote NPC assembly at the end of mitosis.

Holzer G , De Magistris P , Gramminger C , Sachdev R , Magalska A , Schooley A , Scheufen A , Lennartz B , Tatarek-Nossol M , Lue H , Linder MI , Kutay U , Preisinger C , Moreno-Andres D , Antonin W .

During mitotic exit, thousands of nuclear pore complexes (NPCs) assemble concomitant with the nuclear envelope to build a transport-competent nucleus. Here, we show that Nup50 plays a crucial role in NPC assembly independent of its well-established function in nuclear transport. RNAi-mediated downregulation in cells or immunodepletion of Nup50 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 for NPC interaction. Surprisingly, neither NPC interaction nor binding of Nup50 to importin α/β, the GTPase Ran, or chromatin is crucial for its function in the assembly process. Instead, an N-terminal fragment of Nup50 can stimulate the Ran GTPase guanine nucleotide exchange factor RCC1 and NPC assembly, indicating that Nup50 acts via the Ran system in NPC reformation at the end of mitosis. 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, whereas excess RCC1 can compensate the loss of Nup50.

PubMed ID: 34725842
PMC ID: PMC8634129
Article link: EMBO J
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: nup153 nup35 nup50 nup62 ran rcc1
GO keywords: GTPase activity [+]
Antibodies: Nup50 Ab1 Nup62 Ab3

Article Images: [+] show captions
References [+] :
Aksenova, Nucleoporin TPR is an integral component of the TREX-2 mRNA export pathway. 2020, Pubmed