Light-regulated RNA interference induced by p-hydroxyphenacyl-modified siRNA in mammalian cells.

siRNA is an important tool for modulating gene expression in current biomedical research. It would be highly desirable for siRNA to respond to an external stimulus. In this paper, we report a convenient, photolabile caging agent to regulate siRNA functions. 2-bromo-4'-hydroxyacetophenone (BHAP) can readily modify phosphorothioate backbones and inhibit siRNAs. Mild UV irradiation will cleave the modifying moiety to generate natural nucleic acid backbones, thus activating siRNA functions. Such modification is conveniently conducted in an aqueous solution with high efficiency and is cost-effective and scalable. This approach provides a convenient tool for the controlled regulation of gene expression by deploying minimal usage of complex organic synthesis for site-specific installation of the caging group to siRNA unlike previous reported works that required a series of intricate organic synthesis and cumbersome purification techniques to achieve similar aims. This study will open new doors for optochemical regulation of a variety of genes by pHP caging group in mammalian cell culture.