Enhanced light-activated RNA interference using phosphorothioate-based dsRNA precursors of siRNA

To improve light-activated RNA interference by incorporating phosphorothioate linkages into the dsRNA used. The rationale behind this approach is that the groups have the potential to improve nuclease stability and therefore prevent cleavage of photolabile groups from the RNA termini prior to photolysis.

Photolabile groups (di-methoxy nitro phenyl ethyl or DMNPE) were incorporated into multiple double-stranded precursors of siRNA (dsRNA) that had six, two or no phosphorothioate linkages at the 3' and 5' ends of the strands. They were analyzed for their ability to toggle light-activated RNA interference with light and for serum stability.

Incorporation of phosphorothioate linkages increased serum stability of all dsRNA examined. Presence of DMNPE groups reduced overall stability of the modified RNA relative to the analogous species without DMNPE modification. DMNPE-modified dsRNA with two phosphorothioate linkages in each strand significantly improved the window of expression toggled by light.

Incorporating phosphorothioate groups into dsRNA both stabilizes them towards degradation by serum enzymes, as well as improves them as the basis for light-activated RNA interference.