P{hs-yA.P501T.I538K} expresses the same zinc finger nuclease encoded by P{hs-yA} except for substitution of sequences encoding Threonine for Proline at residue 501 and Lysine for Isoleucine at residue 538. The P501T substitution corrects a missense mutation to give the wild type FokI sequence and the I538K substitution prevents homodimerization of the zinc finger nuclease. The construct was generated in a Casper-based vector.