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An activating mutation in the ATP binding site of the ABL kinase domain
1Leukaemia Research Fund Centre, Institute of Cancer Research, Chester Beatty Laboratories, Fulham Road, London, SW3 6JB United Kingdom.
Abstract:
A number of structural alterations have been shown to activate the leukemogenic potential of the ABL oncogene, but there is little understanding of the regulatory mechanisms that are subverted by such changes. We have used directed mutagenesis to examine a potential regulatory motif in cABL, which could directly influence ABL tyrosine kinase activity. A tyrosine to phenylalanine substitution within the ATP binding fold of the ABL kinase domain is sufficient to activate cABL enzymatic activity, and the mutant protein will alleviate growth factor dependence when expressed in the BA/F3 cell line. This growth promotion is dependent upon the structure of the amino terminus of the protein, and the ABL mutation will cooperate with certain BCR sequences in BCR/ABL fusion proteins to deregulate ABL kinase activity.
Insights
Altering a specific tyrosine in the ABL oncogene activates its leukemogenic potential. This mutation, affecting ABL tyrosine kinase activity, bypasses growth factor dependence and cooperates with BCR sequences.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Structural alterations in the ABL oncogene can activate its leukemogenic potential.
- Regulatory mechanisms subverted by these alterations are poorly understood.
Purpose of the Study:
- To investigate a potential regulatory motif in cABL influencing ABL tyrosine kinase activity.
- To elucidate how specific mutations impact ABL oncogene function.
Main Methods:
- Directed mutagenesis was employed to create specific alterations in cABL.
- The functional impact of mutations was assessed in the BA/F3 cell line.
Main Results:
- A tyrosine to phenylalanine substitution in the ATP binding fold of the ABL kinase domain activates cABL enzymatic activity.
- The mutant protein alleviates growth factor dependence in BA/F3 cells.
- This growth promotion is dependent on the amino terminus structure and cooperates with BCR sequences in BCR/ABL fusion proteins.
Conclusions:
- A specific mutation within the ABL kinase domain is sufficient to activate its oncogenic potential.
- The N-terminus and BCR fusion partners modulate the activity of mutated ABL.
- Understanding these mechanisms is crucial for targeting ABL-driven leukemias.