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Blood, 1 October 2007, Vol. 110, No. 7, pp. 2600-2609. Prepublished online as a Blood First Edition Paper on May 30, 2007; DOI 10.1182/blood-2006-01-028647.
NEOPLASIA NPM/ALK binds and phosphorylates the RNA/DNA-binding protein PSF in anaplastic large-cell lymphoma1 Department of Clinical Medicine, University of Milano-Bicocca, Monza, Italy; 2 Department of Experimental Oncology, The National Cancer Institute of Milan, Milan, Italy; 3 Dipartimento di Biotecnologie (DIBIT), San Raffaele Scientific Institute, Milan, Italy; 4 Molecular Genetics and Microbiology, University of Texas at Austin, TX; 5 Department of Experimental Oncology, The European Institute of Oncology, Milan, Italy; 6 Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, Oxford, United Kingdom; 7 Microscopy and Image Analysis Consortium, Department of Neuroscience, University of Milano-Bicocca, Monza, Italy; 8 Department of Biological Chemistry, Institute of Neuroscience of the Italian National Research Council (CNR), Section of Padua, University of Padua, Italy; 9 Department of Microbiology, Immunology, Virology, and Medical Genetics, Human Cancer Genetics Program and The Ohio State University Comprehensive Cancer Center, Columbus; 10 Department of Oncology, McGill University, Montreal, QC, Canada The oncogenic fusion tyrosine kinase nucleophosmin/anaplastic lymphoma kinase (NPM/ALK) induces cellular transformation in anaplastic large-cell lymphomas (ALCLs) carrying the t(2;5) chromosomal translocation. Protein-protein interactions involving NPM/ALK are important for the activation of downstream signaling pathways. This study was aimed at identifying novel NPM/ALK-binding proteins that might contribute to its oncogenic transformation. Using a proteomic approach, several RNA/DNA-binding proteins were found to coimmunoprecipitate with NPM/ALK, including the multifunctional polypyrimidine tract binding proteinassociated splicing factor (PSF). The interaction between NPM/ALK and PSF was dependent on an active ALK kinase domain and PSF was found to be tyrosine-phosphorylated in NPM/ALK-expressing cell lines and in primary ALK+ ALCL samples. Furthermore, PSF was shown to be a direct substrate of purified ALK kinase domain in vitro, and PSF Tyr293 was identified as the site of phosphorylation. Y293F PSF was not phosphorylated by NPM/ALK and was not delocalized in NPM/ALK+ cells. The expression of ALK fusion proteins induced delocalization of PSF from the nucleus to the cytoplasm and forced overexpression of PSF-inhibited proliferation and induced apoptosis in cells expressing NPM/ALK. PSF phosphorylation also increased its binding to RNA and decreased the PSF-mediated suppression of GAGE6 expression. These results identify PSF as a novel NPM/ALK-binding protein and substrate, and suggest that PSF function may be perturbed in NPM/ALK-transformed cells.
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| Copyright © 2007 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||||