Polyadenylation analysis of hERG1USO transcripts by RACE-PAT. A, schematic outlining the strategy for analyzing poly(A) tail status by RACE-PAT. Reverse transcription using an oligo(dT) anchor primer can occur anywhere along the stretch of poly(A) tail, generating cDNA products of variable length. Primers: F1, hERG1USO specific forward primer; R1, reverse primer before the intron 9 poly(A) signal; R2, reverse primer of the anchor sequence without oligo(dT). B, polyacrylamide gel electrophoresis of PCR products. Lane 1, PCR with F1 and R1 primers. Lane 2, PCR with F1 and R2. C, sequence analysis of a representative clone that contains an 88-adenosine poly(A) tail.