Fig. 1.

Biochemical definition of src, the first oncogene. Panels A and B, above, are from the original PNAS paper by Duesberg and Vogt (1). They show electropherograms of the 60–70S RNAs from two transforming strains of RSV, Schmidt-Ruppin (SR) and B77, before (A) and after (B) heat-dissociation. Insets in A show the final sucrose gradient purification of the RNAs before electrophoretic analysis. The heat-dissociated RNAs were resolved into two subunits with lower (a) and higher (b) electrophoretic mobility. Analyses of biologically cloned viruses revealed that the larger subunit represents the genomic RNA of transforming RSV, whereas the b subunit is the genome of transformation-defective (td) mutants spontaneously segregating from RSV (1, 10). Subsequent mapping studies (10, 11) confirmed that the genomes of RSV and of td mutants share all replicative genes (gag, pol, env) and that the size difference (a − b = x) is caused by the additional src gene at the 3′ end of the RSV genome. Cells infected by RSV become transformed (indicated by rounding) and produce virus progeny (red star symbols), whereas td RSV replicates (green star symbols) but does not transform the host cell. A and B reproduced with permission from ref. 1.