Blondel-Tepaz E, Leverve M, Sokrat B, Paradis JS, Kosic M, Saha K, Auffray C, Lima-Fernandes E, Zamborlini A, Poupon A, Gaboury L, Findlay J, Baillie GS, Enslen H, Bouvier M, Angers S, Marullo S, Scott MGH

Mdm2 antagonizes the tumor suppressor p53. Targeting the Mdm2-p53 interaction represents an attractive approach for the treatment of cancers with functional p53. Investigating mechanisms underlying Mdm2-p53 regulation is therefore important. The scaffold protein ?-arrestin2 (?-arr2) regulates tumor suppressor p53 by counteracting Mdm2. ?-arr2 nucleocytoplasmic shuttling displaces Mdm2 from the nucleus ...

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to the cytoplasm resulting in enhanced p53 signaling. ?-arr2 is constitutively exported from the nucleus, via a nuclear export signal, but mechanisms regulating its nuclear entry are not completely elucidated. ?-arr2 can be SUMOylated, but no information is available on how SUMO may regulate ?-arr2 nucleocytoplasmic shuttling. While we found ?-arr2 SUMOylation to be dispensable for nuclear import, we identified a non-covalent interaction between SUMO and ?-arr2, via a SUMO interaction motif (SIM), that is required for ?-arr2 cytonuclear trafficking. This SIM promotes association of ?-arr2 with the multimolecular RanBP2/RanGAP1-SUMO nucleocytoplasmic transport hub that resides on the cytoplasmic filaments of the nuclear pore complex. Depletion of RanBP2/RanGAP1-SUMO levels result in defective ?-arr2 nuclear entry. Mutation of the SIM inhibits ?-arr2 nuclear import, its ability to delocalize Mdm2 from the nucleus to the cytoplasm and enhanced p53 signaling in lung and breast tumor cell lines. Thus, a ?-arr2 SIM nuclear entry checkpoint, coupled with active ?-arr2 nuclear export, regulates its cytonuclear trafficking function to control the Mdm2-p53 signaling axis.

Date: Dec. 01, 2020

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