Apoptosis or programmed cell death is a highly controlled, universal cellular process of cells. Dysregulation of apoptosis has been linked to several diseases such as cancer. Alzheimers disease and Huntinton's chorea. The process of apoptosis induces translation shutoff which is likely to be mediated by cleavage of certain initiation factors and phosphorylation of other regulatory factors, and which is also likely to be crucial for the completion of cellular killing. Studies will be performed in vitro in cell extracts or with purified recombinant proteins or in vitro in tissue culture cells to elucidate the various modifications which occur in translation regulatory factors and their specific effects on translation activity during apoptosis. Efforts will focus on eukaryotic translation initiation factor 4G (eIF4G) and poly(A)binding protein (PABP) which are crucial factors which control translation initiation rates and modulate 5'-3' interactions between mRNA ends. Preliminary evidence provided shows that both eIF4G and PABP are cleaved at the time during development of apoptosis when protein synthesis is being shutoff in the cells. Experiments will determine if cleavage destroys or modulates the ability of eIF4G and PABP to function in all or only some translation reactions and/or if 5'-3' interactions are disrupted. Further, we hypothesize that cap- independent translation of crucial regulatory proteins whose mRNAs contain internal ribosomal entry sites (IRES) will be capable of continued translation after cleavage of eIF4G. IRES control elements found on certain viral and cellular genes will be subcloned into various expression vectors and tested for translational efficiencies in vitro and in vivo under various conditions of apoptosis or factor-cleavage. The long term goal is to understand how events during apoptosis lead to cell death and further our basic understanding of how protein synthesis is regulated in human cells.
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