Illegitimate recombinations between c-myc and immunoglobulin loci are remodeled by deletions in mouse plasmacytomas but not in Burkitt's lymphomas.

Recombinations between c-myc and immunoglobulin loci are a hallmark of Burkitt's lymphomas and mouse plasmacytomas. Analyzing the fine structure of these illegitimate rearrangements has revealed differences between the recombinations in these two tumors. Recombinations are nearly reciprocal in Burkitt's lymphomas, whereas in most BALB/c plasmacytomas large stretches of c-myc sequences have been deleted. The recombinations detected during preneoplastic development of plasmacytomas, in contrast, have most of the c-myc sequences retained on either one of the translocated chromosomes. We conclude that initial recombination structures are subjected to secondary changes in mouse plasmacytomas. In Burkitt's lymphomas the primary recombination sequence is preserved in tumor cells.