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RNA binding by the Wilms tumor suppressor zinc finger proteins
A Caricasole1, A Duarte, S H Larsson
1Cancer Research Campaign Growth Factors, Department of Zoology, University of Oxford, United Kingdom.
Abstract:
The Wilms tumor suppressor gene WT1 is implicated in the ontogeny of genito-urinary abnormalities, including Denys-Drash syndrome and Wilms tumor of the kidney. WT1 encodes Kruppel-type zinc finger proteins that can regulate the expression of several growth-related genes, apparently by binding to specific DNA sites located within 5' untranslated leader regions as well as 5' promoter sequences. Both WT1 and a closely related early growth response factor, EGR1, can bind the same DNA sequences from the mouse gene encoding insulin-like growth factor 2 (Igf-2). We report that WT1, but not EGR1, can bind specific Igf-2 exonic RNA sequences, and that the zinc fingers are required for this interaction. WT1 zinc finger 1, which is not represented in EGR1, plays a more significant role in RNA binding than zinc finger 4, which does have a counterpart in EGR1. Furthermore, the normal subnuclear localization of WT1 proteins is shown to be RNase, but not DNase, sensitive. Therefore, WT1 might, like the Kruppel-type zinc finger protein TFIIIA, regulate gene expression by both transcriptional and posttranscriptional mechanisms.
Insights
The Wilms tumor suppressor gene (WT1) regulates gene expression by binding to DNA and RNA. WT1
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- The Wilms tumor suppressor gene (WT1) is crucial for genitourinary development.
- WT1 encodes proteins regulating gene expression via DNA binding.
- WT1 and EGR1 bind similar DNA sequences, including those in insulin-like growth factor 2 (Igf-2).
Purpose of the Study:
- To investigate WT1's RNA-binding capabilities.
- To determine the role of WT1's zinc fingers in RNA interaction.
- To explore WT1's potential dual transcriptional and posttranscriptional regulatory mechanisms.
Main Methods:
- RNA binding assays to assess WT1-RNA interactions.
- Analysis of WT1 zinc finger domains in RNA binding.
- Subnuclear localization studies using RNase and DNase treatments.
Main Results:
- WT1 binds specifically to Igf-2 exonic RNA sequences, unlike EGR1.
- WT1 zinc fingers are essential for RNA binding, with zinc finger 1 being particularly important.
- WT1's subnuclear localization is sensitive to RNase but not DNase, suggesting RNA involvement.
Conclusions:
- WT1 possesses RNA-binding activity, mediated by its zinc fingers.
- WT1 may regulate gene expression through both DNA and RNA interactions.
- These findings suggest a novel posttranscriptional regulatory role for WT1 in development.