How does the Philadelphia chromosome activate an oncogene?

Question

Quizplus · Accepted Answer

The Philadelphia chromosome is a reciprocal translocation between chromosomes 9 and 22 that fuses the BCR (breakpoint cluster region) gene on chromosome 22 with the ABL (Abelson) gene on chromosome 9, creating a fusion gene called BCR-ABL. The ABL gene is a proto-oncogene that encodes a protein tyrosine kinase involved in cell signaling pathways. When it fuses with the BCR gene, which has a strong promoter, the resulting BCR-ABL fusion protein is constitutively active and promotes uncontrolled cell proliferation, leading to the development of chronic myelogenous leukemia (CML). Thus, the Philadelphia chromosome activates an oncogene (ABL) by fusing it with another protein (BCR) and altering its activity.

How Does the Philadelphia Chromosome Activate an Oncogene