Expression of enhanced levels of small RNA polymerase III transcripts encoded by the B2 repeats in simian virus 40-transformed mouse cells

Although specific viral genes are known which are sufficient to transform certain types of cells, viral transformation has been shown to he accompanied by a change in the level of expression of cellular genes. Assuming that this latter class of genes is involved in some way in the establishment of the transformed state, we and others1,2 have sought to characterize them. To this end, we constructed a complementary DNA library from a simian virus 40 (SV40)-transformed mouse cell line and screened this library for induced genes. Here we focus on the characterization of a specific cDNA clone called 10λ5. We show that the clone 10λ5 contains a B2 repeat3,4, and that the levels of the small heterogeneously sized B2 cytoplasmic RNAs homologous to 10λ5 are enhanced in transformed cells. Our studies show that these RNAs are a specific class of polymerase III transcripts containing a highly conserved 5′ end. SV40 transformation results, therefore, in the activation of specific polymerase III transcripts as well as specific polymerase II transcripts.