title: c-Myc sensitizes cells to tumor necrosis factor-mediated apoptosis by inhibiting nuclear factor kappa B transactivation.
abstract: Nuclear factor kappaB (NF-kappaB) plays a key role in suppression of tumor necrosis factor (TNF)-mediated apoptosis by inducing a variety of anti-apoptotic genes. Expression of c-Myc has been shown to sensitize cells to TNF-mediated apoptosis by inhibiting NF-kappaB activation. However, the precise step in the NF-kappaB signaling pathway and apoptosis modified by c-Myc has not been identified. Using the inducible c-MycER system and c-Myc null fibroblasts, we found that expression of c-Myc inhibited NF-kappaB activation by interfering with RelA/p65 transactivation but not nuclear translocation of NF-kappaB. Activation of c-Myc promoted TNF-induced release of cytochrome c from mitochondria to the cytosol because of the inhibition of NF-kappaB. Furthermore, we found that NF-kappaB-inducible gene A1 was attenuated by expression of c-Myc and that the restoration of A1 expression suppressed c-Myc-induced TNF sensitization. Our results elucidate the molecular mechanisms by which c-Myc increases cell susceptibility to TNF-mediated apoptosis, indicating that c-Myc may exhibit its pro-apoptotic activities by repression of cell survival genes.
authors.affiliation: Laboratory of Molecular Signaling and Apoptosis, Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Zongbing
authors.initials: Z
authors.lastname: You
authors.forename: Lee V
authors.initials: LV
authors.lastname: Madrid
authors.forename: Daniel
authors.initials: D
authors.lastname: Saims
authors.forename: John
authors.initials: J
authors.lastname: Sedivy
authors.forename: Cun-Yu
authors.initials: CY
authors.lastname: Wang
mesh_terms: D021581:Active Transport, Cell Nucleus; D017209:Apoptosis; D015153:Blotting, Western; D002470:Cell Survival; D003574:Cytochrome c Group / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D003574:Cytochrome c Group; D016328:NF-kappa B; D016271:Proto-Oncogene Proteins c-myc; D014409:Tumor Necrosis Factor-alpha; D008156:Luciferases