Exon 8 was replaced with a modified one in which nucleotide substitutions (CACACCTAC to GCCGCGGCA) resulted in the amino acid substitution of three alanines for histidine, threonine and tyrosine at positions 350 to 352 (HTY350-352AAA). These mutations disrupt the subnuclear targeting/co-factor interaction domain. Cre-mediated recombination removed the floxed neomycin resistance cassette inserted upstream of the modified exon 8. (J:214025)