Figure 1.

Construction of plasmids used. (A) Conventional plasmid encoding cancer-testis antigen SSX2 (pTVG-SSX2), as previously described.²⁷ (B) Minicircle DNA (DMC-SSX2) harboring an identical transgene expression cassette as pTVG-SSX2, created using the pMC.CMV-MCS-SV40polyA minicircle production vector and the ΦC31 integrase sensitive ZYCY10P3S2T E. coli strain (System Biosciences). (C) Mini-intronic plasmid encoding SSX2 (MIP-SSX2), obtained upon cloning of an OIPR intron containing a modified bacterial origin of replication, exonic splicing enhancers and a selectable RNA-OUT marker (Nature Technology Corporation), into a unique restriction site downstream of the CMV promoter in the DMC-SSX2 construct (as previously described).²⁰