Figure 3. PCR on genomic DNA of sT-ag-positive cell clones revealed the sT-ag is not directly DNA-encoded. PCR / RT-PCR analyses of genomic DNA (lanes 1–3)/cellular RNA (lanes 4–6) of strongly (clones 2 and 7) and weakly (clone 5) expressing rat 2 cell clones. RT-PCR using primers g and w detected in all clones a 462 nt band resulting from the spliced T-ag mRNA as well as a 609 nt band related to the sT-ag mRNA, which was distinct in clones 2 and 7 and faint in clone 5. PCR from the genomic DNA detected in all clones a 808 nt band, which corresponds to the regular distance of the primer binding sites on the integrated SV40 DNA. A 955 nt (808 nt + 147 nt) PCR product relating to a direct genomic DNA template for sT-ag mRNA synthesis, e.g., as a result of a DNA rearrangement with a partial 147 nt SV40 DNA duplication, was not observed.