A 2ND TRANSCRIPTIONALLY ACTIVE DNA-BINDING SITE FOR THE WILMS-TUMOR GENE-PRODUCT, WT1

The putative Wilms tumor suppressor gene, wt1, encodes a zinc-finger p rotein that binds to the DNA sequence 5'-GCGGGGGVG-3'. We previously r eported that WT1 has separable domains that function either to activat e or suppress transcription. We now have identified a second WT1 bindi ng sequence (5'-TCCTCCTCCTCCTCTCC-3') 3' to the transcription initiati on site of the platelet-derived growth factor A-chain gene by DNase I footprinting and gel mobility shift assays. WT1 requires both 5' and 3 ' binding sites for transcriptional suppression; however, WT1 function s as a transcriptional activator when it binds to either the 5' or 3' site alone. This second WT1 binding sequence functions equally well as the previously identified 5'-GCGGGGGCG-3' sequence when analyzed in t ransient transfection assays. A core DNA sequence recognized by WT1 wa s defined by using related synthetic oligonucleotides. We also identif ied sequences similar to the WT1 binding site within the promoter regi ons of five other growth-related genes and demonstrated that each of t hese sequences also binds WT1 in gel mobility shift assays. These resu lts thus identify a second WT1 binding site and suggest that additiona l growth-related genes may be transcriptionally influenced by WT1.