Insertion of Excised IgH Switch Sequences Causes Overexpression of Cyclin D1 in a Myeloma Tumor Cell

Summary may function as locus control regions (LCR)—down-stream of each a gene, that is, Ea1 and Ea2 (Chen Oncogenes are often dysregulated in B cell tumors and Birshtein, 1997; Mills et al., 1997). Therefore, unlike as a result of a reciprocal translocation involving an excised V(D)J intervening sequences, excised human immunoglobulin locus. The translocations are caused IgH switch intervening sequences generated by recom- by errors in two developmentally regulated DNA re- bination between switch sequences upstream and down- combination processes: V(D)J and IgH switch recom- streamofEa1(e.g.,recombinationbetweenSm andSg2, bination. Both processes share the property of joining Sg4, Se,orSa2) will contain Ea1. If excised switch re- discontinuous sequences from one chromosome and combination sequences containing Ea1 were to inte- releasing intervening sequences as circles that are grate at another chromosomal site, one can predict that lost from progeny cells. Here we show that these in-