OVERLAPPING RNA AND DNA-BINDING DOMAINS OF THE WT1 TUMOR-SUPPRESSOR GENE-PRODUCT

The Wilms' tumour suppressor gene (wt1) is mutated in a subset of pati ents with Wilms' tumour and has a critical role in urogenital developm ent, wt1 encodes a zinc finger transcription factor which regulates ex pression of several genes involved in cellular proliferation and diffe rentiation. Although a number of studies have characterized the DNA bi nding properties of the WT1 protein, recent evidence has suggested tha t WT1 may also have a role in RNA metabolism. We have used an RNA sele ction method to identify WT1 binding ligands from a random RNA pool, T h ree groups of RNA ligands specifically recognized by WT1 were identi fied. Mutational analysis pinpointed ribonucleotide sequences critical for binding. Analysis of truncated WT1 proteins demonstrated that thr ee of four zinc fingers were necessary for RNA-protein interaction. Th e naturally occurring WT1 isoforms with insertion of lysine, threonine and serine between zinc fingers three and four were unable to bind th e selected RNAs. The selected RNA ligands competed with the cognate WT 1 DNA binding site for complex formation with WT1, Our findings sugges t potential cellular RNA target sequences for WT1 and provide tools fo r studying the structural and functional properties of this tumour sup pressor protein.