Cloning and sequencing of 3 breakpoints occurring in MTS1^bcrα. Top: Schematic representation of the 36-kb deletion that brings sequences 5′ to MTS2 exon 1 (MTS2^bcr1 ) upstream to MTS1 exon 1α. (▪) MTS1 exons; (□) MTS2 exons. Vertical arrows represent breakpoints. Insert: Hybridization with junction-specific oligonucleotides after direct PCR amplification of T39p, T117, and T127 breakpoints with OL16 and OL1. PCR products were analyzed in a 2% agarose, 2% NuSieve gel, transferred on a hybond N⁺ membrane, and successively hybridized with ³²P-radiolabeled oligonucleotide specific for junctional sequences of T39p (AJ T39p), T117 (AJ T117), and T127 (AJ T127) and with a common internal oligoprobe, OL15. C-, negative control (no DNA). Bottom: Nucleotide sequence alignment of T39p, T117, and T127 rearrangements with germline chromosome 9 sequences. Canonic heptamers are boxed, and putative N regions are underlined. No consensus nonamer was found. However, highly degenerated nonamers may be present at 23 bp from the MTS2^bcr1 heptamer and at 12 bp from the MTS1^bcrα heptamer. Localization of breakpoints on germline sequences is indicated by arrows.