A 45-year-old man presents with fatigue, left upper quadrant fullness, and splenomegaly on examination. Complete blood count shows WBC 180,000/μL with left shift (myelocytes, metamyelocytes, and bands present), basophilia 8%, and hemoglobin 9.2 g/dL. Bone marrow biopsy confirms chronic myeloid leukemia with t(9;22) Philadelphia chromosome. The structure marked **C** in the diagram is responsible for the pathogenesis of this disease. Which of the following best describes the mechanism by which this structure drives unrestrained myeloid proliferation?