Electrophoretic analysis of the molecular weight of murine mammary tumor virus RNA

Molecular weight determinations of native and subunit RNAs of murine mammary tumor virus (MuMTV), a type B oncornavirus, were performed by polyacrylamide gel electrophoresis and compared with molecular weights of well-characterized avian cellular RNAs and tobacco mosaic virus RNA. From extrapolations of semilog plots of the molecular weights of the standard RNAs versus relative electrophoretic mobilities and Ferguson plots, the subunit and native RNAs of MuMTV were found to possess molecular weights of 2.93 X 10(6) and 6.45 X 10(6), respectively. These data support the assumption that two subunit molecules comprise the native RNA of MuMTV.