Researchers including Feng Zhang have confirmed that a bacterial protein hypothesized as a tool for targeted editing of RNA, similar to how CRISPR-Cas9 targets DNA, can indeed be used as an alternate editing approach. The finding holds important implications for a range of biological applications, such as marking, modifying and modulating RNA. Roughly half of all bacteria species utilize an immune system called the Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated genes (CRISPR-Cas), which protects the microbes from viruses and other invading DNA. While much focus in recent years has been directed at the ability to harness CRISPR-Cas systems to edit DNA, systems that specifically target RNA have been less studied. Here, Zhang and colleagues build on previous work to characterize the behavior of a new type of CRISPR-CAS system, C2c2, suspected to target RNA. Through a series of experiments, the researchers demonstrate that C2c2 can be used to cleave single-stranded RNA, but not double-stranded RNA; as well, it can be used to knockout messenger RNA of bacteria in vivo. In testing the ability of C2c2 to target specific RNA in Escherichia coli, the team found that it initially focuses on its target RNA, followed by a second phase in which it degrades RNA in a less specific way. Other RNA-targeting immune systems likely exist, the authors say, and further research will lead to the development of programmable molecular tools for in vivo RNA manipulation. One example includes modulating RNA function and translation, which could be used for large-scale screening of biological molecules, construction of synthetic regulatory circuits and other purposes, the authors say.