Figure 1.

Cloning the genomic breakpoints involved in the tandem duplication of ALL1 exons 2–6. (A) The wild-type ALL1 gene is normally composed of 36 exons. For the purposes of this figure, only exons 1–16 are shown. In this study, all breakpoints occurred within intron 6 of the 11q23 bcr and within a discrete region near the 3′ end of intron 1, indicated as intron 1 bcr. Tandem duplication of ALL1 exons 2–6 results from a fusion of intron 6 with intron 1 in a 5′ to 3′ direction. This is indicated by the fusion of the solid bar with the open bar. The fusion region is enlarged to show the location of PCR primers 6.1 and 2.0R and restriction sites used for cloning the breakpoints. E, EcoRI; H, HindIII. (B) Alu elements and breakpoints involved in the tandem duplication of ALL1 exons 2–6. Intron 6 is 1.7 kb long and contains four full-length Alu elements, as represented by the solid boxes. Open arrows in the boxes indicate the orientation of the Alu elements. The location of the breakpoint for each case is indicated by a vertical arrow and corresponding patient number. The breakpoints of patients 24 and 350 are only one nucleotide apart and are indicated by the same arrow. The intron 1 bcr is 3.8 kb and contains 2 Alu elements (boxes d and f), and four shorter portions of Alu elements (boxes a, b, c, and e). Solid arrows in the boxes indicate their orientation. The location of the breakpoint for each case is indicated by the vertical arrow and corresponding patient number.