Nucleophosmin interaction with APE1: Insights into DNA repair regulation

• Published in: DNA repair 2020-04, Vol.88, p.102809-102809, Article 102809
• Main Authors: López, David J., de Blas, Ander, Hurtado, Mikel, García-Alija, Mikel, Mentxaka, Jon, de la Arada, Igor, Urbaneja, María A., Alonso-Mariño, Marián, Bañuelos, Sonia
• Format: Article
• Language: English
• Subjects: APE1; Base excision repair; BER; NPM1; Nucleophosmin; Protein-protein interaction
• ISSN: 1568-7864; 1568-7856
• DOI: 10.1016/j.dnarep.2020.102809

NPM1 (pentameric, with core domain depicted in blue and C-terminal domains in yellow) can bind several molecules of APE1 (green) and compete with the off-target, low-affinity binding of APE1 to a model of substrate DNA, thus favouring the specific binding of APE1 to the abasic site (red circle) (a). After incision, turn-over of APE1 could be facilitated by NPM1, which would act as a chaperone reservoir (b). [Display omitted] •Upon oxidative damage, nucleophosmin is recruited to chromatin regions, as APE1.•Subnuclear dynamics of NPM1 correlates with phosphorylation at T199.•Pentameric NPM1 binds several APE1 molecules.•NPM1 favours specific binding of APE1 to abasic DNA, thus helping catalysis. Nucleophosmin (NPM1), an abundant, nucleolar protein with multiple functions affecting cell homeostasis, has also been recently involved in DNA damage repair. The roles of NPM1 in different repair pathways remain however to be elucidated. NPM1 has been described to interact with APE1 (apurinic apyrimidinic endonuclease 1), a key enzyme of the base excision repair (BER) pathway, which could reflect a direct participation of NPM1 in this route. To gain insight into the possible role(s) of NPM1 in BER, we have explored the interplay between the subnuclear localization of both APE1 and NPM1, the in vitro interaction they establish, the effect of binding to abasic DNA on APE1 conformation, and the modulation by NPM1 of APE1 binding and catalysis on DNA. We have found that, upon oxidative damage, NPM1 is released from nucleoli and locates on patches throughout the chromatin, perhaps co-localizing with APE1, and that this traffic could be mediated by phosphorylation of NPM1 on T199. NPM1 and APE1 form a complex in vitro, involving, apart from the core domain, at least part of the linker region of NPM1, whereas the C-terminal domain is dispensable for binding, which explains that an AML leukemia-related NPM1 mutant with an unfolded C-terminal domain can bind APE1. APE1 interaction with abasic DNA stabilizes APE1 structure, as based on thermal unfolding. Moreover, our data suggest that NPM1, maybe by keeping APE1 in an “open” conformation, favours specific recognition of abasic sites on DNA, competing with off-target associations. Therefore, NPM1 might participate in BER favouring APE1 target selection as well as turnover from incised abasic DNA.