All cells are confronted with DNA damage, for example by exposure of the skin to UV rays, chemical byproducts of nerve cells consuming sugar, or immune cells destroying bacteria. If these DNA lesions are not - or badly - repaired, they may initiate tumor formation. Thankfully, cells have evolved an elaborate control system to correct these DNA anomalies. Uli Rass and Nico Thomä at the FMI, together with colleagues at the University of Geneva (UNIGE), have now discovered the key role of a protein called Rif1 in the protection, stabilization and repair of damaged DNA. This study, published in the journal Nature Structural & Molecular Biology, uncovers a DNA maintenance function likely to be present in all eukaryotes because the region of Rif1 that enables the formation of a protective sheath around DNA lesions is similar in humans and yeast.