Physical Interaction between Wilms Tumor 1 and p73 Proteins Modulates Their Functions

Volkher Scharnhorst,Patrick Dekker,Alex J Van Der Eb,Aart G Jochemsen

doi:10.1074/jbc.275.14.10202

Volkher Scharnhorst, Patrick Dekker + Show 2 more

Open Access

https://doi.org/10.1074/jbc.275.14.10202

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Abstract

The WT1 gene, which is heterozygously mutated or deleted in congenital anomaly syndromes and homozygously mutated in about 15% of all Wilms tumors, encodes tissue-specific developmental regulators. Through alternative mRNA splicing, four main WT1 protein isoforms are synthesized. All isoforms can bind to DNA via their zinc fingers, albeit with different affinities and specificities, and thereby modulate the transcriptional activity of their target genes. Several proteins bind to and alter the transcription regulatory properties of the WT1 proteins, including the product of the tumor suppressor gene p53. Interaction between WT1 and p53 was shown to modulate their ability to regulate the transcription of their respective target genes. Here, we report that all four isoforms of WT1 bind to p73, a recently cloned homologue of p53. p73 binds to the zinc finger region of WT1 and thereby inhibits DNA binding and transcription activation by WT1. Similarly, WT1 inhibits p73-induced transcription activation in reporter assays and counteracts p73-induced expression of endogenous Mdm2. This, taken together with our finding that WT1 also interacts with p63/KET, another p53 homologue, suggests that association between WT1 and the members of the p53 family of proteins may be an important determinant of their functions in cell growth and differentiation.

Highlights

Wilms tumor or nephroblastoma is the most common pediatric malignancy and arises from a metanephric blastema cell that fails to undergo cell cycle arrest and differentiation [1]
It was thought that all four WT1 protein isoforms function exclusively as transcription factors, but increasing evidence suggests that the WT1 isoforms containing the KTS splice insert may be involved in post-transcriptional processing of RNA (16 –18)
The binding between WT1 and p73/p53 is most likely direct and does not require additional proteins, since in vitro translated-WT1 molecules bind to purified p73␣ and p53 in GST pull-down assays. p73 inhibits DNA binding by WT1 and represses WT1-mediated transcription activation from a luciferase reporter construct

Summary

Introduction

Wilms tumor or nephroblastoma is the most common pediatric malignancy and arises from a metanephric blastema cell that fails to undergo cell cycle arrest and differentiation [1]. WT1 inhibits p73-mediated transcription activation of reporter constructs and attenuates p73-induced expression of endogenous Mdm2.

Results

Conclusion