Cloning of breakpoints in 3q21 associated with hematologic malignancy

Rearrangements of band 3q21 have been well documented in leukemia. To analyze the region involved, we have isolated a normal genomic P1 clone that spans the 3q21 breakpoints derived from two leukemia patients carrying t(3;3)(q21;q26). Both breakpoints are contained within a 50-kb NotI restriction fragment, but are not identical. They are separated by 9-11 kb and may disrupt genes associated with either the proximal or distal NotI sites. We further show that one patient carried a small insertion of material from chromosome 2 in the 3q- derivative. The P1 clone will allow isolation of candidate genes for these breakpoints and investigations into the clustering of other 3q21 leukemia breakpoints.