BCR(redirected from Breakpoint Cluster Region)
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BCRBreakpoint cluster region. A 5.8-kb DNA segment on chromosome 22q11.23, which, in contrast to the well-studied BCR-ABL fusion protein related to malignant transformation of pluripotent haematopoietic stem cells in CML, encodes a gene product of unknown function, which has serine/threonine kinase activity and is a GTPase-activating protein for p21rac.
In CML there is a reciprocal translocation between chromosome 9q34—a site which contains the human homolog of the Abelson viral oncogene, c-abl—and chromosome 22q1, the location of the breakpoint cluster region; this translocation results in formation of the Philadelphia chromosome, which transcribes a hybrid mRNA, encoding a protein with tyrosine kinase activity.