Figure 2. The domain structure of the 4 WT1 splice variants.
WT1 is a zinc finger transcription factor with 2 distinct sites for RNA splicing. WT1A is the shortest form of WT1, in that it lacks both inserts. WT1B and WT1D contain exon 5 (Ex5), a 17 aa insert located immediately 3’ of the activation domain. In addition, the tripeptide lysine-threonine-serine (KTS) is inserted immediately after zinc finger 3 (ZF3) in both WT1C and WT1D. Amino acids 1-180 are critical for dimerization of WT1, which is a prelude to transcriptional activation; amino acids 84-124 repress WT1 activity by blocking dimerization. Finally, there is a putative RNA Recognition Motif (RRM) near the N-terminus of WT1 thought to contribute to the RNA splicing functions of the KTS+ forms of WT1 (WT1C and WT1D).