BCR gene recombines with genomically distinct sites on band 11Q13 in complex BCR-ABL translocations of chronic myeloid leukemia.

We have analysed a cloned 11q13/3'BCR junction fragment, one recombination product of a complex t(9;11;22) translocation in a patient with chronic myeloid leukemia. 3'M-Bcr recombined with chromosome band 11q13 at a specific point between two Alu elements lying in opposite orientation. We present new molecular data comparing the genomic location of the 11q13 breakpoint in our patient with that of one other recently reported to lie within the GSTP1 gene. This is the first time that specific breakpoint sites within a chromosomal region highly involved in complex Ph translocations have been relatively mapped. These early results argue against a precise site in 11q13 with which M-Bcr preferentially recombines and favour instead a larger recombination-prone domain. Both of the 11q13 breakpoint regions show Alu repeat elements in close proximity to the site of recombination.