The WT1 gene product stabilizes p53 and inhibits p53-mediated apoptosis.

Abstract

The Wilms' tumor-suppressor gene product WT1 coimmunoprecipitates with p53 from baby rat kidney (BRK) cells and Wilms' tumor specimens, and expression of WT1 in BRK cells is associated with increased levels of endogenous wild-type p53 protein. To study the effect of WT1 on p53 function, we cotransfected expression constructs into Saos-2 cells, an osteosarcoma cell line without endogenous expression of either gene. Expression of WT1 resulted in increased steady-state levels of p53, attributable to a prolongation in protein half-life, and associated with protection against papillomavirus E6-mediated degradation of p53. This effect mapped to zinc fingers 1 and 2 of WT1 and was not observed with the closely related EGR1 protein. The stabilized p53 demonstrated enhanced binding to its target DNA sequence and increased trans-activation of a promoter containing this RGC site, but reduced transcriptional repression of a TATA-containing promoter lacking this site. Expression of WT1 inhibited p53-mediated apoptosis triggered by UV irradiation or by expression of temperature-sensitive p53 in the wild-type conformation, but did not affect p53-mediated cell cycle arrest. We conclude that WT1 protein can stabilize p53, modulate its trans-activational properties, and inhibit its ability to induce apoptosis. This effect may contribute to the elevated levels of wild-type p53 protein that are observed in Wilms' tumors.

Twenty years of p53 research: structural and functional aspects of the p53 protein

“…Thus, modulation of RB and E2F through p53 signalling in response to DNA damage may play a central role in deciding the choice between cell cycle and arrest. Moreover, it has been shown that the Wilms tumor suppressor gene product, WT1, binds p53 and inhibits p53-dependent apoptosis without a ecting p53-dependent growth arrest, also revealing a determining mechanism for p53 downstream events (Maheswaran et al, 1995).…”

The DNA binding domains of the WT1 tumor suppressor gene product and chimeric EWS/WT1 oncoprotein are functionally distinct

“…These results have two implications: (i) they argue that the integrity of WT1 zinc ®nger I is essential in maintaining par-4 interaction, and (ii) the abolishment of par-4 binding to EWS/WT1 may contribute to the oncogenic potential of this fusion product, since par-4 binding to EWS/WT1 could be expected to prevent activation by the NTD-EWS domain. The p53 gene product can also associate with WT1 via its zinc ®ngers (Maheswaran et al, 1995). We have not assessed whether this association is maintained with EWS/WT1 chimeric products, but its disruption could also be important to the mechanism of transformation by EWS/WT1.…”

E1B 55K sequesters WT1 along with p53 within a cytoplasmic body in adenovirus-transformed kidney cells

“…Stable cell lines expressing adenovirus 5 E1A (6.1 cells) and E1A plus E1B (10.2 cells) have been described elsewhere (Haber et al, 1992;Maheswaran et al, 1993Maheswaran et al, , 1995. To map the WT1 interaction domains, 10.2 cells were stably transfected by calcium phosphate transfection with CMV-driven, HA-tagged WT1 deletion constructs, which have been previously described .…”