A loxP site was inserted into intron 56 and an FRT site flanked neomycin resistance gene cassette followed by a second loxP site was inserted into intron 58. Sequence encoding 61 of the 121 amino acids of the SET domain were thus enclosed within loxP sites. Subsequent Cre-mediated recombination resulted in the loss of exons 57-58, including sequence encoding the RYINHS motif, which contributes to the catalytic core region of the SET domain. (J:116064)