PROTEIN TYROSINE PHOSPHATASE RECEPTOR-TYPE O TRUNCATED (PTPROt) REGULATES SYK PHOSPHORYLATION, PROXIMAL B-CELL RECEPTOR SIGNALING AND CELLULAR PROLIFERATION Running title: PTPROt regulates SYK activity and BCR signaling

Linfeng Chen, Przemyslaw Juszczynski, Kunihiko Takeyama, Ricardo C.T. Aguiar, Margaret A. Shipp Division of Hematologic Malignancies, Dana-Farber Cancer Institute, Boston, MA Corresponding author: Margaret A. Shipp, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, phone 617-632-3874, Fax 617-632-4734, email: margaret_shipp@dfci.harvard.edu Word count: 3151 Scientific heading: Immunobiology Blood First Edition Paper, prepublished online August 3, 2006; DOI 10.1182/blood-2006-03-013821