Finally, we show that in t(X;1)(p11;q21)-positive renal tumor cells several processes that link PRCCTFE3 expression to p21((WAF1/CIP1))-mediated cell cycle delay are abrogated.     ///    "This delay, which is mediated by induction of the cyclin-dependent kinase inhibitor p21((WAF1/CIP1)), affects both the G1/S and the G2/M phases of the cell cycle and prevents the cells from undergoing polyploidization. "    ///    We also show that the PRCCTFE3 fusion protein binds directly to the p21((WAF1/CIP1)) promoter and that the PRCCTFE3-induced up-regulation of p21((WAF1/CIP1)) leads to activation of the pRB pathway. 