Domain-dependent function of the rasGAP-binding protein p62Dok in cell signaling.
p62Dok, the rasGAP-binding protein, is a common target of protein-tyrosine kinases. It is one of the major tyrosine-phosphorylated molecules in v-Src-transformed cells. Dok consists of an amino-terminal Pleckstrin homology domain, a putative phosphotyrosine binding domain, and a carboxyl-terminal tail containing multiple tyrosine phosphorylation sites. The importance and function of these sequences in Dok signaling remain largely unknown. We have demonstrated here that the expression of Dok can inhibit cellular transformation by the Src tyrosine kinase. Both the phosphotyrosine binding domain and the carboxyl-terminal tail of Dok (in particular residues 336-363) are necessary for such activity. Using a combinatorial peptide library approach, we have shown that the Dok phosphotyrosine binding domain binds phosphopeptides with the consensus motif of Y/MXXNXL-phosphotyrosine. Furthermore, Dok can homodimerize through its phosphotyrosine binding domain and Tyr(146) at the amino-terminal region. Mutations of this domain or Tyr(146) that block homodimerization significantly reduce the ability of Dok to inhibit Src transformation. Our results suggest that Dok oligomerization through its multiple domains plays a critical role in Dok signaling in response to tyrosine kinase activation.
Songyang
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Verna and Marrs Mclean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA. songyang@bcm.tmc.edu
Yamanashi
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Y
Liu
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D
Baltimore
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D
D016475:3T3 Cells; D000818:Animals; D002471:Cell Transformation, Neoplastic; D004268:DNA-Binding Proteins; D020549:GTP Phosphohydrolase Activators / Q000378:metabolism*; D051379:Mice; D010748:Phosphopeptides / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D016601:RNA-Binding Proteins; D015398:Signal Transduction; D020703:ras GTPase-Activating Proteins / Q000378:metabolism*
D004268:DNA-Binding Proteins; C489561:Dok1 protein, mouse; C074561:GAP-associated protein p62; D020549:GTP Phosphohydrolase Activators; D010748:Phosphopeptides; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D020703:ras GTPase-Activating Proteins; D016392:Proto-Oncogene Proteins pp60(c-src)