FIG. 1.

Viral RNA species expressed in MuLV-infected cells. Cellular RNA from mock-infected cells or cells acutely infected with wt Friend MuLV or the FDV mutant (see Fig. 2) were analyzed by Northern blot hybridization with a radiolabeled probe complementary to the 3′ MuLV region (nt 5638 to 8327). This probe reveals the viral genomic RNA (8.3 kb), the single-spliced env RNA (3 kb), and a third RNA species (4 to 5 kb). Positions of RNA molecular size markers and 28S and 18S ribosomal RNAs are indicated.