Homology between an endogenous viral LTR and sequences inserted in an activated cellular oncogene

Recently, some of us reported the detection and molecular cloning of a rearranged cellular oncogene, designated rc-mos, from a non-virally-induced mouse myeloma, XRPC24. Recombinant lambda phage DNA containing the rc-mos gene was active in transforming NIH 3T3 cells in a transfection assay, whereas recombinant DNA containing the unrearranged c-mos gene was not. In rc-mos, coding sequences from the 5' end of c-mos were found to have been displaced by a novel cellular element whose nucleotide sequence was reported. We now document the fact that a 349-base pair (bp) segment of the novel DNA immediately adjacent to the retained c-mos sequences in rc-mos has close homology with the long terminal repeat (LTR) of a known intracisternal A-particle gene. This homology was mentioned in Nature recently after it had been brought to the attention of the editors (N. Hozumi and R. Hawley, personal communication).