Cloning and sequencing of a t(14;19) breakpoint that involves the C mu switch region

The t(14;19) is a recurring translocation found in a small number of cases of chronic B-cell leukemia (CLL). We have cloned and sequenced the breakpoint in a patient with a t(14;19) and shown that the breakpoint on chromosome 14 occurred in the C mu switch region, and that the breakpoint on chromosome 19 occurred in the 5' untranslated region of the BCL3 gene. This is in contrast to all the other reported cases with a t(14;19) in which the breakpoints on chromosome 14 occurred in the C alpha 1 or C alpha 2 switch region, and the breakpoints on chromosome 19 occurred upstream of the BCL3 gene. Our results further emphasize the importance of the switch region in the t(14;19) translocation.