Determination of poly (A) tail length. Total RNAs extracted from 24 hours post-transfected Hela-cells were ligated with the anchor primer RVP3 oligo. First strand cDNA synthesis was carried with an antisense sequence to the anchor primer. To detect poly (A) tail length, the transcripts derived from Rec5-L and R7f-L were then selectively amplified using the forward primer for viral U3 sequences of the 3’ LTR and the reverse primer for the RVP3 sequence. To confirm that the first strand of cDNA that was synthesized with an anti-RVP3 oligo strand contained spliced luciferase-mRNA, PCR was performed using the primer set of f-597 and s2. As a control, the gapdh-mRNA and poly (A) tail length of gapdh-mRNA were detected in Rec5-L and R7f-L transfected cells. The PCR products were electrophoresed and visualized by ethidium-bromide staining.