title: Synergistic and opposing regulation of the stress-responsive gene IEX-1 by p53, c-Myc, and multiple NF-kappaB/rel complexes.
abstract: NF-kappaB/rel proteins, tumor suppressor p53, and oncogene c-Myc are critical transcription factors involved in coordinating cellular decision-making events in response to external stimuli. Consensus sequences for binding these three transcription factors are found in the promoter region of IEX-1 (Immediate Early response gene X-1) gene that can either suppress or induce apoptosis in a cell- and stimulus-dependent manner. Utilizing an electrophoretic mobility shift assay (EMSA) and a promoter/reporter assay, we show that the NF-kappaB/rel consensus sequence in the IEX-1 promoter is specifically bound and activated by multiple NF-kappaB/rel complexes in descending order p65-c-rel-->p65-50-->p50-50. Interestingly, NF-kappaB/rel-mediated activation of IEX-1 expression was synergized by p53, but strongly inhibited by c-Myc in a dose-dependent fashion. Moreover, the ability of c-Myc to inhibit IEX-1 expression requires the presence of functional p53, which may partially contribute to the varying effects of p53 on IEX-1 expression in different cells. In support of coordinated regulation of IEX-1 expression by these three transcription factors in vivo, binding of endogenous p53, c-Myc and NF-kappaB/rel proteins, including p50, p65 and c-rel, to the IEX-1 promoter was demonstrated in living cells by chromatin immunoprecipitation using specific antibodies. The study reveals a novel integrative regulation of specific gene expression by NF-kappaB/rel, p53 and c-Myc transcription factors.
mesh_terms: D051017:Apoptosis Regulatory Proteins; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics*; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000235:genetics*; D008565:Membrane Proteins; D016328:NF-kappa B / Q000502:physiology*; D052002:NF-kappa B p50 Subunit; D009363:Neoplasm Proteins; D009687:Nuclear Proteins / Q000502:physiology; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology; D051996:Transcription Factor RelA; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: D051017:Apoptosis Regulatory Proteins; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; D015534:Trans-Activators; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53