Subcellular localization of the proteins implicated in DNA damage-induced cell death

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Apoptosis or programmed cell death is a physiologic process that is regulated by evolutionarily conserved genes. Dysregulation of apoptosis can contribute to many major diseases including cancer, autoimmune disorders and certain neurodegenerative diseases. DNA damage-induced apoptosis is accomplished by proapoptotic members of the Bcl-2 family, such as Bim, and a family of cysteine proteases termed caspases. During the period of two years we got the results as follows.We have cloned and characterized six novel isoforms of human Bim, designated as Bimα1, α2, and β1-β4, which are generated by alternative splicing. Among the novel isoforms, only Bimα1 and α2 contained a BH3 domain and were proapoptotic, although less potent than the classical isoforms. These two isoforms localized, at least in part, in mitochondria. Expression profiles of bim isoforms were highly variable among normal tissues at least in humans, suggesting a tissue-specific transcriptional regulation of bim.Caspase-8 and -10 can induce NF-κB activation in protease-independent manner. Investigation of the signaling pathways leading to caspase-8 and -10-mediated NF-κB activation using the GST pull-down assay revealed that, among upstream kinases that activate NF-κB, NIK and RIP, but not RICK or IKKα/β could directly bind to caspase-8and -10. By using dominant-negative mutants and small interfering RNA technology, we also demonstrated that NIK and IKKα are required for this process.