E1B 55K SEQUESTERS WT1 ALONG WITH P53 WITHIN A CYTOPLASMIC BODY IN ADENOVIRUS-TRANSFORMED KIDNEY-CELLS

WT1 encodes a tumor suppressor that is expressed in cells of the devel oping kidney and is inactivated in Wilms tumor, a pediatric kidney can cer. The adenovirus E1B 55K gene product contributes to the transforma tion of primary baby rat kidney (BRK) cells by binding and inactivatin g the product of the p53 tumor suppressor. We have previously demonstr ated that WT1 and p53 are present within a protein complex in vivo. We non show that WT1 is physically associated with E1B 55K in adenovirus -transformed cells, an interaction that is mediated by the first two z inc fingers of WT1. Immunodepletion of p53 abrogates the coimmunopreci pitation of E1B 55K and WT1, consistent with the presence of a trimeri c protein complex containing these three proteins. In the presence of E1B 55K, WT1 which is normally localized in the nucleus, is retained w ithin a very high molecular weight complex and sequestered in the char acteristic perinuclear cytoplasmic body that contains E1B 55K and p53, Expression of E1B 55K in osteosarcoma cells that undergo apoptosis fo llowing expression of WT1 inhibits WT1-mediated cell death. We conclud e that E1B 55K may target WT1 along with p53, resulting in the functio nal inactivation of both tumor suppressor gene products by this viral oncoprotein.