Phosphate steering by Flap Endonuclease 1 promotes 5′-flap specificity and incision to prevent genome instability

Flap Endonuclease 1 is a DNA replication and repair enzyme indispensable for maintaining genomic stability. Here the authors provide mechanistic details on how FEN1 selects for 5′-flaps and promotes catalysis to avoid large-scale repeat expansion by a process termed ‘phosphate steering’.