Figure 3.
Model for nick-initiated resection by MRN-CtIP at protein-occluded DSBs. Sae2/CtIP activates the MRX/MRN endonuclease activity to generate a nick, followed by bidirectional resection catalyzed by MRN in the 3′ to 5′ direction and EXO1 in the 5′ to 3′ direction.