Src family kinases phosphorylate the Bcr-Abl SH3-SH2 region and modulate Bcr-Abl transforming activity

J Biol Chem. 2006 Oct 13;281(41):30907-16. doi: 10.1074/jbc.M605902200. Epub 2006 Aug 15.


Bcr-Abl is the oncogenic protein-tyrosine kinase responsible for chronic myelogenous leukemia. Recently, we observed that inhibition of myeloid Src family kinase activity (e.g. Hck, Lyn, and Fyn) induces growth arrest and apoptosis in Bcr-Abl-transformed cells, suggesting that cell transformation by Bcr-Abl involves Src family kinases (Wilson, M. B., Schreiner, S. J., Choi, H. J., Kamens, J., and Smithgall, T. E. (2002) Oncogene 21, 8075-8088). Here, we report the unexpected observation that Hck, Lyn, and Fyn strongly phosphorylate the SH3-SH2 region of Bcr-Abl. Seven phosphorylation sites were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry: Tyr89 and Tyr134 in the Abl-derived SH3 domain; Tyr147 in the SH3-SH2 connector; and Tyr158, Tyr191, Tyr204, and Tyr234 in the SH2 domain. SH3 domain Tyr89, the most prominent phosphorylation site in vitro, was strongly phosphorylated in chronic myelogenous leukemia cells in a Src family kinase-dependent manner. Substitution of the SH3-SH2 tyrosine phosphorylation sites with phenylalanine substantially reduced Bcr-Abl-mediated transformation of TF-1 myeloid cells to cytokine independence. The positions of these tyrosines in the crystal structure of the c-Abl core and the transformation defect of the corresponding Bcr-Abl mutants together suggest that phosphorylation of the SH3-SH2 region by Src family kinases impacts Bcr-Abl protein conformation and signaling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Binding Sites
  • Cell Transformation, Neoplastic
  • Fusion Proteins, bcr-abl / chemistry*
  • Humans
  • Mutation
  • Phosphorylation
  • Protein Conformation
  • Protein Structure, Tertiary
  • Signal Transduction
  • Tyrosine / chemistry
  • src Homology Domains
  • src-Family Kinases / chemistry
  • src-Family Kinases / physiology*


  • Tyrosine
  • Fusion Proteins, bcr-abl
  • src-Family Kinases