CRISPR-Cas9 is a customizable tool that lets scientists cut and insert small pieces of DNA at precise areas along a DNA strand. Image credit: Ernesto del Aguila III, NHGRI (CC BY-NC 2.0).
Ribonucleic acid or RNA is an important molecule involved in making proteins, transmitting diseases, offering immunity in form of vaccines, and also degrading itself. Programmed RNA degradation is a common method used by bacteria to protect themselves from invading viruses.
Bacteria acquire viral genetic materials during infections, which are then converted into RNA fragments, or guide RNA. The guide RNAs both locate and recruit enzymes to help destroy the infectious RNA. These programmable RNA degradation machineries can be repurposed for biotechnology applications to help regulate gene expression or to minimize the effect of viral infections.
Similar machineries, like the CRISPR/Cas9 gene editing tool, act like genetic scissors, allowing researchers to make precise modifications to DNA to study and alter the role of genes in the cell. Like in bacteria, the CRISPR system uses fragments of RNA from viruses as a guide to identify matching targets and create breakages in the genetic material. Recently, researchers discovered Cas7-11, which is used to break sections of RNA in viruses.
To better understand how Cas7-11 works, Goswami et al. studied its three-dimensional structure. Detailed views of each segment of the protein, together with biochemical studies of the protein’s activity, helped to identify their respective roles. The structural information also highlighted three regions involved in snipping RNA and revealed how they drive this process. This analysis showed that a short segment of Cas7-11 alone is sufficient to prepare and bind the guide RNA fragments.
These findings add to the understanding of how Cas7-11 prepares its guide and creates breakages in RNA. It has a similar structure to a previously known assembly of proteins that also breaks down RNA, providing insight into its evolution. The detailed analysis of how Cas7-11 works also demonstrates the possibility of engineering it as a laboratory tool to remove specific RNA sequences in cells.
