A neomycin resistance gene cassette replaced 1.1kb of sequence containing exon 2, which encodes the first zinc finger of the DNA binding domain. RT-PCR and Western blot analysis of intestinal tissue from homozygous mice detected the presence of a truncated transcript and protein that appears to use M53 in exon 3 as an initiation site. This truncated protein is able to bind ligand but lacks transactivation activity.