Transforming properties of the Huntingtin interacting protein 1/ platelet-derived growth factor beta receptor fusion protein.
We have previously reported that the Huntingtin interacting protein 1 (HIP1) gene is fused to the platelet-derived growth factor beta receptor (PDGFbetaR) gene in a patient with chronic myelomonocytic leukemia. We now show that HIP1/PDGFbetaR oligomerizes, is constitutively tyrosine-phosphorylated, and transforms the murine hematopoietic cell line, Ba/F3, to interleukin-3-independent growth. A kinase-inactive mutant is neither tyrosine-phosphorylated nor able to transform Ba/F3 cells. Oligomerization and kinase activation required the 55-amino acid carboxyl-terminal TALIN homology region but not the leucine zipper domain. Tyrosine phosphorylation of a 130-kDa protein and STAT5 correlates with transformation in cells expressing HIP1/PDGFbetaR and related mutants. A deletion mutant fusion protein that contains only the TALIN homology region of HIP1 fused to PDGFbetaR is incapable of transforming Ba/F3 cells and does not tyrosine-phosphorylate p130 or STAT5, although it is itself constitutively tyrosine-phosphorylated. We have also analyzed cells expressing Tyr --> Phe mutants of HIP1/PDGFbetaR in the known PDGFbetaR SH2 docking sites and report that none of these sites are necessary for STAT5 activation, p130 phosphorylation, or Ba/F3 transformation. The correlation of factor-independent growth of hematopoietic cells with p130 and STAT5 phosphorylation/activation in both the HIP1/PDGFbetaR Tyr --> Phe and deletion mutational variants suggests that both STAT5 and p130 are important for transformation mediated by HIP1/PDGFbetaR.
Ross
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Division of Hematology/Oncology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Gilliland
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D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D050719:Crk-Associated Substrate Protein; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D007377:Interleukin-3; D015477:Leukemia, Myelomonocytic, Chronic / Q000235:genetics*; D051379:Mice; D008894:Milk Proteins; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D011506:Proteins; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics*; D050717:Retinoblastoma-Like Protein p130; D050799:STAT5 Transcription Factor; D017384:Sequence Deletion; D016608:Talin; D015534:Trans-Activators / Q000378:metabolism
C493841:BCAR1 protein, human; C493842:Bcar1 protein, mouse; D050719:Crk-Associated Substrate Protein; D004268:DNA-Binding Proteins; C073368:HIP1 protein, human; C489536:Hip1 protein, mouse; D007377:Interleukin-3; D008894:Milk Proteins; D010750:Phosphoproteins; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D050799:STAT5 Transcription Factor; D016608:Talin; D015534:Trans-Activators; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor