c-myc gene in a murine plasmocytoma without visible chromosomal translocations moves to chromosome 12F1 with Pvt-1 and rearranges with IgH enhancer-S mu sequences.

The DCPC 21 plasmocytoma lacks any of the MPC-associated chromosomal translocations. However, the c-myc gene has been transposed to the IgH locus on chromosome 12 by an Ig switch-region-mediated recombination mechanism. DNA sequencing analysis, further, revealed that this recombination is consistent with an insertion of the IgH enhancer (E mu)-S mu sequences, 2341 bp in length, into the c-myc 5'-flanking region, resulting in 5': c-myc 5'-flanking-E mu-S mu-c-myc 5'-flanking-c-myc exon-1: 3' segment. In situ molecular hybridization of DCPC 21 metaphase chromosome spreads using a Pvt-1 probe demonstrated that Pvt-1 has also moved to the F1 sub-band region of chromosome 12 where the IgH genes are located. These results indicate that the c-myc gene has been inserted into the IgH locus together with the Pvt-1, regardless of whether plasmocytoma has cytogenetically identifiable translocations. The possible interaction between c-myc activation and Pvt-1 in the development of MPCs is discussed.