Model for MMEJ. Shown is the joining event that is the most frequent in SLY19. Putative end processing of 4-bp 3′ noncomplementary overhangs created by the cleavage of two HO endonuclease recognition sequences will expose the microhomology that mediates annealing. Subsequent 3′-flap removal that is mostly dependent on Rad1-Rad10 will prime the fill-in synthesis and ligation by Dnl4. Microhomologies are shown in boldface. Unpaired 3′ flaps are shown as small letters. The gene products that may function at each step are listed to the right of the arrows.