Isolation of an endogenous C-type RNA virus from Mus musculus molossinus

We isolated a type-C RNA virus from the Japanese field mouse, Mus musculus molossinus. M. musculus musculus and M. musculus molossinus are two different subspecies of Mus and thus only distantly related. The virus grew only on cells foreign to the host, was xenotropic, and readily rescued the murine sarcoma (MuSV) genome from a normal rat kidney cell line transformed nonproductively by the Harvey strain of MuSV. The virus banded at a density of 1.16 g/ml and contained an RNA-dependent DNA polymerase.