title: Tumor necrosis factor-alpha-induced caspase-1 gene expression. Role of p73.
abstract: Tumour necrosis factor-alpha (TNF-alpha) is a cytokine that is involved in many functions, including the inflammatory response, immunity and apoptosis. Some of the responses of TNF-alpha are mediated by caspase-1, which is involved in the production of the pro-inflammatory cytokines interleukin-1beta, interleukin-18 and interleukin-33. The molecular mechanisms involved in TNF-alpha-induced caspase-1 gene expression remain poorly defined, despite the fact that signaling by TNF-alpha has been well studied. The present study was undertaken to investigate the mechanisms involved in the induction of caspase-1 gene expression by TNF-alpha. Treatment of A549 cells with TNF-alpha resulted in an increase in caspase-1 mRNA and protein expression, which was preceded by an increase in interferon regulatory factor-1 and p73 protein levels. Caspase-1 promoter reporter was activated by the treatment of cells with TNF-alpha. Mutation of the interferon regulatory factor-1 binding site resulted in the almost complete loss of basal as well as of TNF-alpha-induced caspase-1 promoter activity. Mutation of the p53/p73 responsive site resulted in reduced TNF-alpha-induced promoter activity. Blocking of p73 function by a dominant negative mutant or by a p73-directed small hairpin RNA reduced basal as well as TNF-alpha-induced caspase-1 promoter activity. TNF-alpha-induced caspase-1 mRNA and protein levels were reduced when p73 mRNA was down-regulated by small hairpin RNA. Caspase-5 gene expression was induced by TNF-alpha, which was inhibited by the small hairpin RNA-mediated down-regulation of p73. Our results show that TNF-alpha induces p73 gene expression, which, together with interferon regulatory factor-1, plays an important role in mediating caspase-1 promoter activation by TNF-alpha.
authors.affiliation: Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: Nishant
authors.initials: N
authors.lastname: Jain
authors.forename: Ch
authors.initials: Ch
authors.lastname: Sudhakar
authors.forename: Ghanshyam
authors.initials: G
authors.lastname: Swarup
mesh_terms: D001483:Base Sequence; D020170:Caspase 1 / Q000235:genetics*; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D009687:Nuclear Proteins / Q000502:physiology*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000502:physiology*
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C000606460:TP73 protein, human; D014409:Tumor Necrosis Factor-alpha; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D020170:Caspase 1