1. ¹Division of Oncology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
2. ²Research Center for Radiation Emergency Medicine, National Institute of Radiological Sciences, Chiba, Japan
3. ³Neuroscience and Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA, USA

Correspondence: Dr T Yamamoto, Division of Oncology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan. E-mail: tyamamot@ims.u-tokyo.ac.jp

Received 12 July 2006; Revised 27 September 2006; Accepted 28 September 2006; Published online 6 November 2006.

Abstract

The t(2;5) chromosomal translocation occurs in anaplastic large-cell lymphoma arising from activated T lymphocytes. This genomic rearrangement generates the nucleophosmin (NPM)-anaplastic lymphoma kinase (ALK) oncoprotein that is a chimeric protein consisting of parts of the nuclear protein NPM and ALK receptor protein-tyrosine kinase. We used yeast two-hybrid screening to identify an adaptor protein Suc1-associated neurotrophic factor-induced tyrosine-phosphorylated target (SNT)-2 as a new partner that interacted with the cytoplasmic domain of ALK. Immunoprecipitation assay revealed that SNT-1 and SNT-2 interacted with NPM-ALK and kinase-negative NPM-ALK mutant. Y156, Y567 and a 19-amino-acid sequence (aa 631–649) of NPM-ALK were essential for this interaction. The interaction through Y156 and Y567 was dependent on phosphorylation of these tyrosines, whereas the interaction through the 19-amino-acid sequence was independent of phosphorylation. NPM-ALK mutant protein mutated at these three binding sites showed significantly reduced transforming activity. This transformation-defective NPM-ALK mutant still interacted with signal transducing proteins such as phospholipase C-gamma and phosphatidylinositol 3-kinase, which were previously reported to be relevant to NPM-ALK-dependent tumorigenesis. These observations indicate that the three SNT-binding sites of NPM-ALK are important for its transforming activity. This raises a possibility that SNT family proteins play significant roles in cellular transformation triggered by NPM-ALK, which though remains to be verified.