Insertion of several different DNAs in reticuloendotheliosis virus strain T suppresses transformation by reducing the amount of subgenomic mRNA.

The highly oncogenic retrovirus reticuloendotheliosis virus (Rev) strain T (Rev-T) has, relative to its helper virus Rev strain A, a substitution of the oncogene v-rel for most of the env gene and a large deletion of gag and pol sequences. When the helper virus sequences that are deleted in Rev-T are replaced, the recombinant virus is nontransforming (I. S. Y. Chen and H. M. Temin, Cell 31: 111-120, 1982). We show that suppression of transformation occurs when several different DNA sequences are inserted in Rev-T and that suppression is correlated with a reduction in the amount of v-rel mRNA and v-rel protein in infected cells. The reduced amount of v-rel protein is insufficient for transformation.