title: Ionizing radiation-inducible apoptosis in the absence of p53 linked to transcription factor EGR-1.
abstract: The tumor suppressor protein p53 is a pivotal regulator of apoptosis, and prostate cancer cells that lack p53 protein are moderately resistant to apoptotic death by ionizing radiation. Genes encoding the transcription factor early growth response-1 (EGR-1) and cytokine tumor necrosis factor-alpha (TNF-alpha) were induced upon irradiation of prostate cancer cells, and inhibition of EGR-1 function resulted in abrogation of both TNF-alpha induction and apoptosis. Induction of the TNF-alpha gene by ionizing radiation and EGR-1 was mediated via a GC-rich EGR-1-binding motif in the TNF-alpha promoter. Because TNF-alpha induces apoptosis in prostate cancer cells, these findings suggest that, in the absence of p53, ionizing radiation-inducible apoptosis is mediated by EGR-1 via TNF-alpha transactivation.
authors.affiliation: Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky 40536, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Ahmed
authors.forename: S F
authors.initials: SF
authors.lastname: Sells
authors.forename: K
authors.initials: K
authors.lastname: Venkatasubbarao
authors.forename: S M
authors.initials: SM
authors.lastname: Fruitwala
authors.forename: S
authors.initials: S
authors.lastname: Muthukkumar
authors.forename: C
authors.initials: C
authors.lastname: Harp
authors.forename: M
authors.initials: M
authors.lastname: Mohiuddin
authors.forename: V M
authors.initials: VM
authors.lastname: Rangnekar
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D051766:Early Growth Response Protein 1; D006801:Humans; D017874:Immediate-Early Proteins; D017404:In Situ Hybridization, Fluorescence; D016297:Mutagenesis, Site-Directed; D011836:Radiation Tolerance / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D015854:Up-Regulation; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53