| In the current study we show that the Retinoblastoma susceptibility protein ( Rb ) protein interacts with Bag 1 , an apoptotic regulator , in human colonic adenoma and carcinoma derived cell lines . ^^^ Coimmunoprecipitation demonstrated that endogenous Rb and Bag 1 interact in both adenoma and carcinoma derived cell lines . ^^^ The specificity of the interaction was demonstrated by expression of human Papillomavirus E 7 oncoprotein , an inhibitor of Rb protein interactions , which disrupted the Rb / Bag 1 complex . ^^^ Disruption of the Rb / Bag 1 complex through expression of E 7 changes the subcellular distribution of Bag 1 , decreasing nuclear localised Bag 1 . ^^^ Our work establishes that the Rb protein interacts with the Bag 1 apoptotic regulator protein , and introduces a novel function for Rb , involving modulation of the subcellular localisation of Bag 1 in human colonic epithelial cells . . ^^^ |