CRKL binding to BCR-ABL and BCR-ABL transformation

The SH2-SH3 domain-containing adaptor protein CRKL is the predominant tyros ine phosphorylated protein in chronic myelogenous leukemia (CML) neutrophil s and BCR-ABL-expressing cell lines. The amino terminal CRKL SH3 domain bin ds directly to a proline-rich region in the C-terminus of BCR-ABL. BCR-ABL mutants with deletions of this region were constructed to assess biologic e ffects of eliminating the CRKL binding site. Yeast two-hybrid analysis and gel overlay assays show eradication of the direct interaction of CRKL with BCR-ABL in the proline deletion mutants. However, these BCR-ABL mutants tra nsform myeloid cells to growth factor independence, and in these cells CRKL is tyrosine phosphorylated and associates with BCR-ABL. These findings sug gest both direct and indirect interactions of CRKL, with BCR-ABL. Thus, dis ruption of the direct interaction with BCR-ABL has not excluded a role for CRKL in BCR-ABL-mediated transformation.