Light-regulated mRNA condensation by a photosensitive surfactant works as a series photoswitch of translation activity in the presence of small RNAs.

AzoTAB, a photosensitive azobenzene cationic surfactant, which phototriggers translation activity through light-regulated condensation of mRNA, is added to a translation solution containing several mRNAs, which can be selectively silenced by specific small RNAs. We find that gene silencing by small RNAs remains functional regardless of AzoTAB concentration and UV illumination. In the absence of UV, the translation of all genes present in the medium is partially to fully inhibited depending on AzoTAB concentration. In contrast, the application of a short UV stimulus (365 nm for 1.5 min) results in the selective photoactivation of genes that are not silenced by small RNA. These results show that light-regulated condensation by AzoTAB works as a sequence-independent series photoswitch added to parallel sequence-specific regulation by small RNAs.