The eyDBD::Cas9 entry in FlyBase represents a fusion protein in which a Cas9 RNA-guided nuclease (derived from the naturally occurring Cas9 endonuclease from Streptococcus pyogenes and in which the two nuclease domains present in the naturally occurring protein are functional) is fused to the DNA-binding domain from the D. melanogaster ey gene. The presence of the ey DNA-binding domain recruits DNA fragments containing the 3xP3 regulatory sequence to Cas9-induced double-stranded DNA breaks, enhancing their incorporation upon DNA repair (FBrf0245562).