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Blood, 15 February 2004, Vol. 103, No. 4, pp. 1445-1453. Prepublished online as a Blood First Edition Paper on October 9, 2003; DOI 10.1182/blood-2003-07-2452.
NEOPLASIA Identification and characterization of EBP, a novel EEN binding protein that inhibits Ras signaling and is recruited into the nucleus by the MLL-EEN fusion proteinFrom the Department of Pathology and Department of Biochemistry, The University of Hong Kong; and Department of Pathology, Stanford University, Palo Alto, CA.
The chimeric MLL-EEN fusion protein is created as a result of chromosomal translocation t(11;19)(q23;p13). EEN, an Src homology 3 (SH3) domaincontaining protein in the endophilin family, has been implicated in endocytosis, although little is known about its role in leukemogenesis mediated by the MLL-EEN fusion protein. In this study, we have identified and characterized EBP, a novel EEN binding protein that interacts with the SH3 domain of EEN through a proline-rich motif PPERP. EBP is a ubiquitous protein that is normally expressed in the cytoplasm but is recruited to the nucleus by MLL-EEN with a punctate localization pattern characteristic of the MLL chimeric proteins. EBP interacts simultaneously with EEN and Sos, a guanine-nucleotide exchange factor for Ras. Coexpressoin of EBP with EEN leads to suppression of Ras-induced cellular transformation and Ras-mediated activation of Elk-1. Taken together, our findings suggest a new mechanism for MLL-EENmediated leukemogenesis in which MLL-EEN interferes with the Ras-suppressing activities of EBP through direct interaction.
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