Laboratory investigation uncovers Dok-2 as a RasGAP-binding protein in BCR-ABL-expressing cells, indicating a novel signaling adapter family involved in chronic myelogenous leukemia.
Key Points
To identify and characterize novel downstream substrate proteins of the oncogenic p210(bcr-abl) tyrosine kinase in chronic myelogenous leukemia.
Purified and cloned cDNA for the 56-kDa tyrosine-phosphorylated protein p56(dok-2) from cells expressing p210(bcr-abl).
Characterized structural motifs and RasGAP-binding properties, analyzed tissue distribution of mRNA, and queried expressed sequence tag databases for related genes.
Cloned human dok-2 cDNA encoding a 412-amino acid signaling molecule with an N-terminal pleckstrin homology domain, six PXXP motifs, 13 potential tyrosine phosphorylation sites, and p120(RasGAP) binding activity.
Demonstrated that Dok-2 shares 35% sequence identity with p62(dok-1) and identified at least four additional Dok-homology family members in expressed sequence tag databases.
Found dok mRNAs predominantly expressed in tissues of hematopoietic origin, supporting their role as downstream mediators of p210(bcr-abl).