To generate swarms of new viral particles, a virus hijacks a cell into producing masses of self-assembling cages that are then loaded with the genetic blueprint for the next infection. But the picture of how that DNA is loaded into those viral cages, or capsids, was blurry, especially for two of the most common types of DNA virus on earth, bacterial viruses and human herpesvirus. Jefferson researchers pieced together the three-dimensional atomic structure of a doughnut-shaped protein that acts like a door or ‘portal’ for the DNA to get in and out of the capsid, and have now discovered that this protein begins to transform its structure when it comes into contact with DNA. Their work published today in Nature Communications.