Nucleophosmin Is Required for DNA Integrity and p19 Arf Protein Stability
Authors: Raffaella Zamponi
Paola Martinelli
Kristian Helin
Emanuela Colombo
Pier Giuseppe Pelicci
Jean-Christophe Marine
Eros Lazzerini Denchi
Brunangelo Falini
Paola Bonetti
Journal: Molecular and Cellular Biology (2005)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: Nucleophosmin; NPM; tumor suppressors; p53; p19(Arf)
Affiliations: Department of Experimental Oncology, European Institute of Oncology, Milan, Italy., Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy, IFOM Institute, Via Adamello 16, 20139 Milan, Italy, Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium, Institute of Hematology and Internal Medicine, University of Perugia, 06100 Perugia, Italy, Department of Medicine, Surgery and Dentistry, University of Milan, Milan, Italy

Abstract:  Nucleophosmin (NPM) is a nucleolar phosphoprotein that binds the tumor suppressors p53 and p19(Arf) and is thought to be indispensable for ribogenesis, cell proliferation, and survival after DNA damage. The NPM gene is the most frequent target of genetic alterations in leukemias and lymphomas, though its role in tumorigenesis is unknown. We report here the first characterization of a mouse NPM knockout strain. Lack of NPM expression results in accumulation of DNA damage, activation of p53, widespread apoptosis, and mid-stage embryonic lethality. Fibroblasts explanted from null embryos fail to grow and rapidly acquire a senescent phenotype. Transfer of the NPM mutation into a p53-null background rescued apoptosis in vivo and fibroblast proliferation in vitro. Cells null for both p53 and NPM grow faster than control cells and are more susceptible to transformation by activated oncogenes, such as mutated Ras or overexpressed Myc. In the absence of NPM, Arf protein is excluded from nucleoli and is markedly less stable. Our data demonstrate that NPM regulates DNA integrity and, through Arf, inhibits cell proliferation and are consistent with a putative tumor-suppressive function of NPM. 

Retracted: No

PubPeer comments:
 Figure 5B and 5D, two bands of Arf (red boxes) look much more similar than expected. The red arrow is pointing at a putative vertical discontinuity. Could the authors please post the uncropped scan of the blots at high resolution and take away any concern? ![file] , 
 Here the scanning of the original blot. Lane 1 and 2 are the controls for the following 6 lanes. In panel B the 4 lanes are contiguous, while in panel D the four lane in between have been removed to facilitate the comparison between the first two (controls) and the last two (cell infected with p19). ![file] , 
 #2 Comment#1  Could the authors please post the uncropped scan of the blots at high resolution and take away any concern? That looks like a cropped scan. You have not addressed the question of the similairity betwen the Arf panels in 5B and 5D, although the accompanying tubulin panels are different. , 
 #2 Dear Dr. Colombo, thank you for posting the raw data. I think this blot indeed takes away the concern on Arf. Last question: tubulin controls are different. Were they run twice for same experiment? Or do they come from different experiments? ,