Myc/Ig juxtaposition by chromosomal translocations: some new insights, puzzles and paradoxes

Human Burkitt's lymphoma and murine plasmacytoma cells contain characteristic chromosomal translocations that show the following common features: ,juxtaposition of the c-myc oncogene to one of the three immunoglobulin loci(2-4); wide variability of the translocation breakpoint in and outside the oncogene, but with rigorous avoidance of any damage to the two coding exons(5-21); high expression of the Ig juxtaposed c-myc gene with concomitant shutdown of the normal, non-translocatedallele(4,7,11,14,15,18). The latter fact suggests that the translocation has removed the oncogene from its normal regulatory circuit andplaced it under the constitutively activating influence of an Ig-locus. This is believed to play an essential role in the malignant transformation(23). Numerous papers have dealt with the possible role of the translocations in tumorigenesis. less attention has been given to their implications with regard to the normal DNA rearrangement process that takes place during B-cell differentiation. In this article, George and Eva Klein consider both areas and their interrelations.