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  • Title: NPM/ALK binds and phosphorylates the RNA/DNA-binding protein PSF in anaplastic large-cell lymphoma.
    Author: Galietta A, Gunby RH, Redaelli S, Stano P, Carniti C, Bachi A, Tucker PW, Tartari CJ, Huang CJ, Colombo E, Pulford K, Puttini M, Piazza RG, Ruchatz H, Villa A, Donella-Deana A, Marin O, Perrotti D, Gambacorti-Passerini C.
    Journal: Blood; 2007 Oct 01; 110(7):2600-9. PubMed ID: 17537995.
    Abstract:
    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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