Nucleotide sequence comparison of normal and translocated murine c-myc genes

Plasmacytoid tumours in mice and Burkitt's lymphomas in humans display characteristic chromosomal translocations involving the c-myc proto-oncogene^1,2. Models to explain quantitative changes in c-myc expression have been proposed based on the loss of normal promoters ^3-9 as a result of translocation. However, alternative explanations^10-16, such as somatic mutation^14,17,18, are needed to explain altered c-myc expression in the absence of gene breakage. We present here the nucleotide sequence of the normal murine c-myc gene. Comparison of this sequence with that of a translocated c-myc gene from a murine plasmacytoma reveals complete identity of coding sequence. One nucleotide difference was found in the non-coding first exon. This shows that qualitative changes of the c-myc gene product are not required for ontogenesis in murine plasmacytomas. In contrast, mutations are found in coding¹⁸ and non-coding¹⁴ regions of translocated c-myc genes from Burkitt's lymphomas, suggesting that the mechanisms by which c-myc is activated in plasmacytomas and Burkitt's lymphomas are different.