title: The ratio of +/-KTS splice variants of the Wilms' tumour suppressor protein WT1 mRNA is determined by an intronic enhancer.
abstract: Alternative splicing of the primary transcript of the Wilms' tumour suppressor gene WT1 involving 2 overlapping 5' splice sites at the end of exon 9 results in the insertion of 2 amino acids (KTS) between zinc fingers 3 and 4 of the protein. The presence or absence of these 3 amino acids has consequences for DNA binding affinity, protein-protein interactions, and subnuclear localization. Disruption of the characteristic +KTS to -KTS ratio of mRNA isoforms as a result of mutations in the +KTS splice site results in Frasier syndrome. Mutational analysis of a WT1 minigene construct was carried out to search for sequences that regulate the +/-KTS alternative splicing event. A strong pyrimidine-rich intronic enhancer that increases the use of the +KTS splice site was identified. Cross-linking experiments with nuclear extracts demonstrated that this enhancer specifically binds a protein with a molecular mass of 42+/-2 kDa. One candidate for this trans-factor is the splicing regulator TIA-1, which binds to the pyrimidine-rich enhancer in the primary transcript from the minigene construct and increases the +/-KTS splicing ratio. The observation that TIA-1 and WT1 are both involved in apoptosis supports our proposal for a functional link between these proteins.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada.
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Romaniuk