Fig. 7.

siRNA targeting of DNA and RNA viruses—role of RNA in the viral life cycle. a Positive-sense RNA viruses, where the viral genome is directly targeted; b double-stranded RNA viruses, where the genome is transcribed by a viral protein to produce the targeted mRNA; c negative-sense RNA viruses, where the genome is transcribed by a viral protein to produce the targeted mRNA; d DNA viruses, which use the host cell transcription factors to produce the targeted mRNA; e retroviruses, similar to positive-sense RNA genomes, where the genome can be directly targeted, or once integrated into the cell DNA, viral mRNA produced can also be targeted