Vectors used for in vitro transcription and mRNAs derived from them. DNA templates coding for the marker proteins eGFP or d2eGFP but varying in (A) linearization site, (B) poly(A) tail length, (C) 3′ untranslated region (UTR), and (D) vectors encoding an ovalbumin-derived T-cell epitope and pp65 protein for investigation of antigen presentation and immune responses were transcribed in vitro in the presence of a cap analog to generate the mRNA species shown on the right.