Molecular analysis of reconstituted mice. (A) Proviral integrants. Ethidium bromide-stained agarose gel showing PCR products amplified from lysates of cells from reconstituted mice or BM cultures. Primers 1 and 2 (Fig 1) were used for amplification of LN-ras2 sequence. Lane 1, ΨLN-ras215 (positive control); lane 2, Nr1 spleen; lane 3, Nr4 thymus; lane 4, Nr5 spleen; lane 5, Nr7 spleen; lane 6, Nr7 lung; lane 7, Nr8 lung; lane 8, Nr8 spleen; lane 9, Nr9 lung; lane 10, LN-ras2–infected BM (in vitro analysis); lane 11, negative control DNA; lane 12, no sample. (B) Proviral expression. Autoradiograph of a Northern blot hybridized to a Ψ region probe (described in Materials and Methods). RNA samples are indicated above each well. Transcript sizes are indicated to the right. The RNA samples on ethidium bromide-stained agarose gels are shown below the autoradiograph. Lane numbers above the gel correspond to the autoradiograph.