1. ¹GSF – National Institute of Health and Environment, Klinische Kooperationsgruppe für Gentherapie, Marchioninistrasse 25, 81377 München, Germany
2. ²Klinikum der Universität München, Medizinische Klinik III, München, Germany
3. ³Genzentrum, Universität München, München, Germany

Correspondence: M Hallek, Klinikum der Universität München, Grohadern, Medizinische Klinik III, Marchioninistrasse 15, 81377 München, Germany; Fax: 0049 89 7095 6039

⁴Present address: Trion Research, Frankfurter Ring 193a, 80807 München, Germany

Received 4 April 2002; Accepted 5 August 2002.

Abstract

Bcr-Abl is found in more than 95% of cases with CML. The mechanism of Bcr-Abl-induced transformation is not fully understood. Bcr-Abl is a constitutively active tyrosine kinase with transforming capacity for hematopoietic cells. We demonstrated recently that the Src kinase Hck interacts directly with Bcr-Abl by a kinase-independent mechanism. Moreover, the inhibition of the Hck kinase seems to block some of the transforming effects of Bcr-Abl. To identify the binding domains mediating this interaction of Hck with Bcr-Abl, we co-expressed different plasmid and baculovirus vectors containing mutants or single domains of Bcr-Abl and/or Hck in COS7 and Sf9 cells. At least four independent binding regions for Hck were identified in Bcr-Abl, one in Bcr, one in the region comprising the SH3 and SH2 domain of Abl, one in the SH1 domain of Abl, and one in the C-terminal domain of Abl. In the Hck kinase, deletion of the SH2 and/or the SH3 region abolished binding to Bcr-Abl. In contrast, deletion of the Hck SH1 domain enhanced binding of Hck to Abl and Bcr-Abl. In conclusion, the results indicate that the interaction of Bcr-Abl with Hck is mediated by a novel, complex mechanism that involves multiple domains of Bcr-Abl and the SH2 and SH3 domains of Hck.