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Expression of Murine N-myc by Insertion of Retrovirus Sequences in a Murine Macrophage Cell Line (RAW264)

RAW264 cells, reported to be originated from Abelson-virus-induced B lymphomas, are widely used as a murine monocyte cell line. We found that RAW264 show enhanced expression of murine N-myc. Murine cDNA clones associated with N-myc were separated from λgt11 cDNA library constructed by using mRNA from the macrophage cell line, RAW264 cells. Sequencing analysis of the longest cDNA clone N-mycL showed that the length of the coding region was 18 bases shorter than that of the predicted full length N-myc cDNA, and the 3′ untranslated region had the 5′ long terminal repeat (LTR) sequence of the Moloney-like proviral sequence, suggesting the expression of N-myc by insertion of the proviral sequence. This suggests that expression of N-myc plays a role in the establishment of macrophage cell line RAW264. Integration of LTR and overexpression of the N-myc gene might have existed in the parental lymphoma cells, playing a role in the development of lymphoma or in the establishment of macrophage cell line.