| Abstract: |
The promyelocytic leukemia protein (PML) is a growth/tumor suppressor essential for induction of apoptosis by diverse apoptotic stimuli. The mechanism by which PML regulates cell death remains unclear. In this study we found that ectopic expression of PML potentiates cell death by apoptosis in the tumor necrosis factor α (TNFα)-resistant cell line U2OS and other cell lines. Treatment with TNFα significantly sensitized these cells to apoptosis in a p53-independent manner. PML/TNFα-induced cell death is associated with DNA fragmentation, activation of caspase-3, -7, and -8, and degradation of DNA fragmentation factor/inhibitor of CAD. PML/TNFα-induced cell death could be blocked by the caspase-8 inhibitors CrmA and c-FLIP but not by Bcl-2. These findings indicate that this cell death event is initiated through the death receptor-dependent apoptosis pathway. PML is a transcriptional repressor of NF-κB by interacting with RelA/p65 and prevents its binding to the cognate enhancer through the C terminus. Coimmunoprecipitation and double-color immunofluorescence staining demonstrated that PML physically interacts with RelA/p65 in vivo and the two proteins colocalized at the endogenous levels. Overexpression of NF-κB rescued cell death induced by PML/ TNFα. Furthermore, PML-/- mouse embryo fibroblasts are more resistant to TNFα-induced apoptosis. Together this study defines a novel mechanism by which PML induces apoptosis through repression of the NF-κB survival pathway. |
| Keywords: |
osteosarcoma; signal transduction; controlled study; protein expression; unclassified drug; human cell; genetics; nonhuman; antineoplastic agents; antineoplastic agent; protein localization; animal cell; mouse; animal; metabolism; animals; mice; cell death; cell survival; gene overexpression; apoptosis; enzyme inhibition; gene expression; nuclear protein; carboxy terminal sequence; embryo; protein degradation; protein dna binding; protein protein interaction; fluorescence; neoplasm proteins; cell line; transcription factor; immunoglobulin enhancer binding protein; genetic transcription; in vivo study; transcription factor rela; caspase 3; enzyme activation; immunofluorescence; tumor cells, cultured; caspase; caspase inhibitor; caspases; protein p53; physiology; animalia; transcription factors; dna strand breakage; nuclear proteins; tumor suppressor gene; chemistry; dna; tumor necrosis factor alpha; tumor necrosis factor-alpha; cell culture; tumors; nf-kappa b; gene repression; tumor suppressor proteins; tumor protein; promyelocytic leukemia; immunoprecipitation; fibroblast; protein structure, tertiary; tumor necrosis factor receptor; caspase 8; receptor; tumor suppressor protein; protein tertiary structure; synaptotagmin; knockout mouse; sensitization; dna fragment; deoxyribonuclease; receptors, tumor necrosis factor; promyelocytic leukemia protein; cells; cell strain u2os; flice inhibitory protein; caspase activated deoxyribonuclease; caspase 7; deoxyribonucleases; color; growth kinetics; pml protein, mouse; pml protein, human; humans; human; priority journal; article; cytokine response modifier a
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