modified iCLIP experiment with the addition of a 5'marker to identify read-through reads

We added an oligonucleotide to the 5' end of RNA fragments —5' marker— to differentiate between truncated and read–through cDNAs. By applying the protocol to PTBP1 and eIF4A3 iCLIP, we determined that the start sites of read–through cDNAs are enriched in adenosines, while the truncated cDNAs preferentially contained thymidines at their starts.