Integrated transposons drive overexpression of <i>Rtl1</i>.

<p>(A) Strand-specific RT-PCR detected activation of <i>Rtl1</i> expression in SB-induced HCCs, with minimal activation of <i>Rtl1as</i> observed. No expression of either transcript was detected in normal liver. (B) Transposons integrated upstream of <i>Rtl1</i> drive its expression by generating fusion transcripts. Transcription initiated from the CAG promoter within the transposon splices into <i>Rtl1</i>, either directly or via inclusion of an upstream cryptic exon. PCR to detect fusion transcripts was performed on cDNA from SB-induced HCCs using the indicated primers. Transposon-driven expression of <i>Rtl1</i> was detected for all of the tumor samples harboring <i>Dlk1-Dio3</i> domain integrations. sd, splice donor.