Figure 5.

Strategies for transgene regulation that combine conditional promoters and splicing cassettes. (A) Concept for promoter stacking with the P5SM splicing cassette. Expression of a single gene is regulated directly by its own promoter (P2) and indirectly by the promoter driving expression of the inducer (P1). Introduction of additional splicing cassettes would enable stacking of more than two promoters. (B) Concept for coordinated regulation of transgenes with the P5SM splicing cassette. A single conditional promoter (P1) drives expression of the inducer, which can target multiple suicide exons. The DNA sequences of the splicing cassettes can be non-homologous, as the recognition element is an RNA structure, to avoid gene silencing. Different constitutive promoters (P2–P4) are used for the individual transgenes, as expression is instead coordinated by conditional alternative splicing.