Structure of the Gateway SINV replicon plasmids pBG60 and pBG78. Transcription of the viral RNA is initiated by the cytomegalovirus immediate early (CMV) promoter and terminated by a polyadenylation signal 3' of the HDV ribozyme (not shown). The hepatitis delta virus (HDV) ribozyme trans-cleaves the RNA, resulting in an authentic 3' RNA end. bsd represents the blasticidin S-deaminase gene. The Gateway attR1/attR2 recombination sites are positioned 3' of the 2nd SGP. CcdB represents E. coli DNA Gyrase poison. Cm(R) represents chloramphenicol acetyltransferase. Recombination of the pBG60 plasmid with pBG76 results in the pBG78 plasmid.