Figure 2. Detection of HERV-K transcripts in 13 cancer cell lines.

RT-PCR was performed to detect viral transcripts at five different positions in HERV-K genome, two of which across splicing junctions to detect RNAs spliced at the conventional env mRNA splice junction (1x-env) and the rec mRNA splice junctions. GAPDH RT-PCR was performed simultaneously and served as a positive control for RNA integrity and as loading comparison. The products were resolved by agarose gel electrophoresis. Genomic positions of the primers used are shown in Fig. 1. Parallel controls were performed without reverse transcriptase (−RT) as controls to exclude DNA contamination. DNA size markers are shown on the left.