What are the properties of the SIRV transcripts’ terminal sequences?

SIRVs as well as ERCCs are in vitro transcription products. Therefore:

• At the 5´end, all RNAs start with a 5' ppp-G, meaning that cap-specific cDNA preparation methods are not feasible.

• At the 3' end, all RNA are polyadenylated (SIRV isoforms and long SIRVs with 30 adenosines, ERCCs with 24 ± 1.05 nt adenosines), enabling oligo(dT) based selection and priming. The SIRVs User Guide contains a graphic representation of the SIRV design.
  

NOTE: You can download the SIRV sequences and reference annotation files from the Lexogen web site at the following location: https://www.lexogen.com/sirvs/download/.