Image: Without FEN1, the protein 53BP1 builds up, hindering DNA repair. In the absence of 53BP1, other pathways take over to remove long DNA flaps and restore DNA integrity. Image credit: Tokyo Metropolitan University Tokyo, Japan – Scientists at Tokyo Metropolitan University have identified a new cellular process that helps protect against the harmful effects of alovudine, a drug used in antiviral and cancer therapies. The research highlights the role of a DNA repair enzyme known as flap