Traditionally, in CRISPR/Cas9 genome editing, scientists use a single-stranded piece of ribonucleic acid (RNA) to guide the Cas9 enzyme to the deoxyribonucleic acid (DNA) they want to target. Instead, Chen and Siu installed a hairpin-like structure that blocks part of the RNA from recognizing the DNA. Only a small part, called the toehold, is exposed and capable of binding to other RNA. Then Chen, and Siu used RNA from within the cell as a trigger to open up their blocking mechanism, activating the Cas9 protein so that it could then bind and regulate the DNA.

“The key thing is that we wanted to use some native cellular information,” said Chen. “We wanted to be able to use this native cellular response as a way to modulate the CRISPR/Cas9 protein functions and basically develop a controlled mechanism so that we could modulate cellular functions accordingly.”

This technology offers a versatile, “plug and play” design that could be used to induce gene editing and regulation in a variety of systems, says Chen.

“Moving forward, the idea is to be able to use, ideally on paper, any kind of cellular messenger RNA as an activation or deactivation device,” he said. “You can imagine that we can activate something based on whether the cells are growing on glucose or starving for phosphate or exposed to high-temperature conditions or low-pH conditions.”

This work was supported by grants from NSF (MCB1615731 and MCB1817675).