Nucleophosmin Protein Dephosphorylation by DUSP3 Is a Fine-Tuning Regulator of p53 Signaling to Maintain Genomic Stability.

Pault Y. M. Ferruzo,Lilian C. Russo,Fabio L. Forti

doi:10.3389/fcell.2021.624933

Pault Y. M. Ferruzo, Lilian C. Russo + Show 1 more

Open Access

https://doi.org/10.3389/fcell.2021.624933

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Abstract

The dual-specificity phosphatase 3 (DUSP3), an atypical protein tyrosine phosphatase (PTP), regulates cell cycle checkpoints and DNA repair pathways under conditions of genotoxic stress. DUSP3 interacts with the nucleophosmin protein (NPM) in the cell nucleus after UV-radiation, implying a potential role for this interaction in mechanisms of genomic stability. Here, we show a high-affinity binding between DUSP3-NPM and NPM tyrosine phosphorylation after UV stress, which is increased in DUSP3 knockdown cells. Specific antibodies designed to the four phosphorylated NPM’s tyrosines revealed that DUSP3 dephosphorylates Y29, Y67, and Y271 after UV-radiation. DUSP3 knockdown causes early nucleolus exit of NPM and ARF proteins allowing them to disrupt the HDM2-p53 interaction in the nucleoplasm after UV-stress. The anticipated p53 release from proteasome degradation increased p53-Ser15 phosphorylation, prolonged p53 half-life, and enhanced p53 transcriptional activity. The regular dephosphorylation of NPM’s tyrosines by DUSP3 balances the p53 functioning and favors the repair of UV-promoted DNA lesions needed for the maintenance of genomic stability.

Highlights

Nucleophosmin (NPM) is a major RNA-associated nucleolar phosphoprotein that contains a central long sequence rich in acidic amino acids with high affinity for silver ions (SchmidtZachmann et al, 1987; Schmidt-Zachmann and Franke, 1988)
When nucleophosmin protein (NPM) expression was evaluated in MRC-5 (NER-proficient) and XPA (NER-deficient) cell lines, silenced for dual-specificity phosphatase 3 (DUSP3) or not (Russo et al, 2020), FIGURE 1 | Dual specificity phosphatase 3 (DUSP3) binds with high affinity to nucleophosmin (NPM) in vitro and affects its nuclear localization and tyrosine phosphorylation. (A) The bimolecular interaction of purified recombinant proteins was performed by Surface Plasmon Resonance (SPR) and the obtained KD# is shown in the graph
DUSP3 affects the expression of certain cyclins, CDKs, and p21Cip1 proteins to regulate cell cycle and proliferation of cells exposed to UV radiation (Russo et al, 2020)

Summary

Introduction

Nucleophosmin (NPM) is a major RNA-associated nucleolar phosphoprotein that contains a central long sequence rich in acidic amino acids with high affinity for silver ions (SchmidtZachmann et al, 1987; Schmidt-Zachmann and Franke, 1988). It is encoded by the NPM gene in a 296-aa long protein exhibiting structurally well-defined C-terminal and N-terminal ends, the latter containing the foremost domains responsible for the pentameric homo-oligomer structure (Hyung et al, 2007; Grummitt et al, 2008). NPM seems to be a promising target in cell sensitization for chemo or radiotherapies (Sekhar et al, 2014), especially because it impacts on the functional regulation of the axis formed by p53, HDM2, and ARF protein (Kurki et al, 2004a,b; Luchinat et al, 2018)

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