Researchers across the globe have increasingly been using a bacterial defence mechanism called CRISPR-Cas9 as a tool to surgically edit DNA in living cells. This new technique has made gene editing a lot easier and more precise. But how these systems function in nature is still not fully understood. Researchers at Delft University of Technology have now determined the role of one of the proteins involved in many CRISPR systems, namely Cas4. As it turns out, this protein helps form ‘memories’ of invading viral elements so that the bacterial cell is protected from virus infection. Virus memories obtained with Cas4 help the cell to find and destroy the invading virus fast enough to survive. The discovery is another important step towards a complete understanding of CRISPR systems. read the whole article