Schematic presentation of the SFV DNA/RNA layered vectors. The plasmid backbone of the vector is not shown; CMV, immediately early promoter of human cytomegalovirus; Rz, hepatitis delta virus negative strand ribozyme; p(A), simian virus 40 late polyadenylation signal. The nsP1-4, region corresponding to ns-proteins of SFV; Luc, coding sequence of the Luc reporter; 26SG, SG-promoter of SFV. Arrows in boldface indicate transcription initiation sites of the CMV and 26SG promoters; bent arrows indicate processing of mRNA transcript by ribozyme and lines indicate noncoding regions of SFV. Sites used for intron insertion are indicated by arrows; inserted introns and thalassemic mutations present in these introns are indicated under the drawings. DNA/RNA layered replicon vector without (A) or with (B) frame-shift (FS) mutation (indicated by arrow) in the region corresponding to the nsP4 gene. EGFP, coding sequence of EGFP reporter. (C) DNA/RNA layered replication-competent vector. "Structural" indicates the region corresponding to structural genes (C-E3-E2-6K-E1) of SFV; wt intron from rabbit beta-globin gene, inserted in this region, is shown by lines above drawing.