title: The Wilms tumour suppressor protein WT1 (+KTS isoform) binds alpha-actinin 1 mRNA via its zinc-finger domain.
abstract: Mutations in WT1 are associated with developmental syndromes that affect the urogenital system and neoplasms, including Wilms tumour, acute myeloid leukemia, and breast and prostate cancers. The WT1 protein belongs to the early growth response family of zinc-finger transcription factors. Uniquely to WT1, an evolutionarily conserved alternative splice event inserts the tripeptide KTS, between zinc fingers 3 and 4. Whereas -KTS isoforms bind DNA and activate or repress transcription, +KTS isoforms bind DNA less efficiently and interact with splice factors and RNA in vitro and in vivo. Although candidate DNA targets have been found, physiological mRNA targets are yet to be defined. We examined the distribution of WT1 in ribonucleoprotein (RNP) complexes in nuclear extract prepared from M15 cells, a mouse mesonephric fetal kidney cell line. WT1 cofractionated with the splice factor PSF in large RNP particles >or=2 MDa. We also found that PSF co-immunoprecipitated with WT1, suggesting a functional interaction between these 2 multifunctional proteins. Using yeast three-hybrid library constructed from the co-immunoprecipitated RNA we found that WT1 (+KTS) binds close to or at the start codon of alpha-actinin 1 (ACTN1) mRNA. A band shift assay confirmed the ability of the WT1 zinc-finger domain (+KTS) to bind this sequence in vitro. ACTN1 is the first likely physiological mRNA target of WT1.
authors.affiliation: Bristol Genomics Research Institute, Faculty of Applied Sciences, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: A A
authors.initials: AA
authors.lastname: Morrison
authors.forename: J P
authors.initials: JP
authors.lastname: Venables
authors.forename: G
authors.initials: G
authors.lastname: Dellaire
authors.forename: M R
authors.initials: MR
authors.lastname: Ladomery
mesh_terms: D000185:Actinin / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002457:Cell Extracts / Q000737:chemistry; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D047468:Immunoprecipitation; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000737:chemistry; D014018:Tissue Distribution; D020798:Two-Hybrid System Techniques; D025721:WT1 Proteins / Q000378:metabolism*; D016335:Zinc Fingers
chemical_list: D002457:Cell Extracts; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D025721:WT1 Proteins; D000185:Actinin