Expression of the adenoviral E1A oncogene induces cells from several species to become sensitive to apoptosis triggered by killer lymphocytes, TNF alpha or chemotherapeutic agents. The mechanism by which E1A induces this sensitization to apoptosis is unknown. E1A mutational analysis data suggest that E1A oncoprotein interactions with the p300 transcriptional coactivator are involved in this mechanism. Activation of the transcription factor, NF-kappa B (NF-kB), for which p300 is a coactivator, can defend cells against apoptosis. Initial data suggest that E1A-p300 interactions repress the injury-induced, NF-kB-dependent cellular defense against injury. However, the mechanism of this E1A-p300 effect on NF-kB activity and its relationship to apoptosis sensitization are undefined. The working hypothesis for this proposal is that E1A sensitizes cells to proapoptotic stimuli by inhibiting injury-induced, NF-kB-dependent transcription through a series of E1A interactions with p300 and other cell cycle regulatory proteins. The objectives of the project are to test the relationships of E1A interactions with p300, Rb-family proteins and cyclin dependent kinases (cdk) to sensitization to apoptotic injury and to define the mechanisms by which these E1A-cell protein interactions repress injury-induced, NF-kB-dependent transcription. Among the interactions to be tested for linkage to this E1A activity are: (1) E1A binding to p300 and Rb-family proteins, (2) E1A-specific stimulation of cdk expression and activity, (3) E1A effects on p300 phosphorylation and p300 binding to NF-kB RelA/p65, and (4) E1A-related effects on RelA/p65 phosphorylation. The long-term objectives are (1) to use E1A as a molecular tool to define the regulatory molecular network that modulates the NF-kB-dependent cellular response to proapoptotic injuries and (2) to test the effects of these E1A-cell protein interactions on injury-induced expression and function of cellular genes which are identified as candidate mediators of the NF-kB cellular defense against apoptosis. The results of these studies may contribute to the understanding of mechanisms of adenoviral release from cells in the inflammatory milieu and may also be useful to identify new approaches through which to enhance cellular responses to immunotherapeutic and chemotherapeutic agents.
