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 (lambda)gt11 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.