Leukemic cells of a patient diagnosed with chronic myeloid leukemia (CML) showed 
a complex BCR-ABL1 rearrangement hidden within a normal appearing karyotype. 
Previous molecular studies had established that the 3' BCR had recombined at a 
novel site within the variable region of the immunoglobulin lambda locus ( IGL). 
A segment of DNA mapping very close to the site of the IGL/3' BCR recombination 
recognized a previously undescribed insertion polymorphism. A combination of 
molecular hybridization studies and long-range polymerase chain reaction was 
used to isolate a 6-kb full-length long interspersed nuclear element (LINE or 
L1), here designated L1(IGL), which occupies 19% of alleles in the general 
population. Although unclonable, DNA sequence analysis by a primer walking 
approach established that L1(IGL) has features characteristic of an actively 
retrotransposing element. The L1(IGL) element has a 5' untranslated region, two 
open reading frames (ORF-1 and ORF-2), a 3' untranslated region and terminates 
in a poly-A tail. We compared the DNA sequence and the predicted amino acid 
sequence of L1(IGL) with a consensus sequence compiled from seven reported 
active L1 elements. This analysis indicated that L1(IGL) has high potential for 
involvement in as yet undetermined somatically and constitutionally acquired 
disease, not only through recombination mechanisms, but also through 
retrotransposition events. This full-length L1 element maps close within the 
IGLlocus to L1.2, one of only nine active L1 elements that have been reported so 
far. L1(IGL) and L1.2 map within a wider and well-recognized region of genomic 
instability on chromosome 22.