The breakpoints of the reciprocal PAX-5translocations in patient MZL-1. The two translocation breakpoints on the derivative chromosomes 14 (A) and 9 (B) were cloned asHindIII DNA fragments and sequenced. Only the relevant sequences across the breakpoints are shown below a schematic diagram of each translocation event. Numbers refer to the corresponding nucleotide positions of the PAX-5 exon 1B (Fig 6B) or immunoglobulin Sμ sequence,28 respectively. Arrows denote the transcription start sites of the antisense promoter in the immunoglobulin Sμ region as determined by Apel et al.28