Fig. 8

Western blot analysis of MMTV particles produced by rat mammary cells (RBA) transiently transfected with pSMt-HYB/D26A-derived constructs containing inactive viral protease. RBA cells expressed wild-type MMTV (WT: lanes 2, 5) and virus with the mutated MA domain of Gag (MA-3N: lanes 3, 6). Lanes 1 and 4 represent samples from mock-transfected cells. At 48 h post-transfection, cells were harvested and directly lysed in SDS protein loading buffer (Cell Lysate). The extracellular virus particles were isolated from culture media by ultracentrifugation through a 20 % sucrose cushion (Medium) and pellets were dissolved in SDS protein loading buffer. Proteins were separated on a 15 % SDS-PAGE gel and detected by Western blot assay using polyclonal anti-MMTV CA antiserum. The migration position of MMTV Gag is indicated