title: Regulation of the expression of caspase-9 by the transcription factor activator protein-4 in glucocorticoid-induced apoptosis.
abstract: Caspase-9 (Casp-9) induces death signals by triggering other types of caspase activation, and its expression greatly influences the onset of apoptosis. During the isolation of apoptosis-related genes involved in glucocorticoid (GC)-induced cell death in murine thymic lymphomas, we found that the antisense gene of the transcription factor activator protein-4 (AP-4) inhibited dexamethasone-induced apoptosis. Western blot analysis revealed that the expression of Bcl-xL, Bax, and Apaf-1 was not affected in cells transfected with sense or antisense AP-4 genes. In contrast, both the expression and activation of Casp-9 were inhibited in the antisense AP-4 transfectants. We isolated the 2.4-kb 5'-flanking region of Casp-9, and the promoter activity was investigated. We found the AP-4-binding sites at -1.55 and -1.38 kb to be responsible for the promoter activity. Furthermore, a negative cis-element was expected to exist between bases -1140 and -944. When the cells were treated with dexamethasone, a rapid down-regulation of AP-4 and Casp-9 was observed whether the cells were GC-sensitive lymphomas or GC-insensitive L929 fibroblast cells. In addition, L929 cells pretreated with dexamethasone were found to be resistant to subsequent treatment with etoposide, an apoptosis-inducing reagent. GC has a two-sided effect on apoptosis, i.e. a pro-apoptotic effect on certain cell types and a prosurvival effect on other cell types. Our findings will explain, at least in part, this effect.
authors.affiliation: Department of Parasitology and Immunology, National Defense Medical College, 3-2 Namiki, Tokorozawa 359-8513, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tsujimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ono
authors.forename: Masaki
authors.initials: M
authors.lastname: Sato
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishida
authors.forename: Takemi
authors.initials: T
authors.lastname: Oguma
authors.forename: Takushi
authors.initials: T
authors.lastname: Tadakuma
mesh_terms: D000818:Animals; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D001665:Binding Sites; D015153:Blotting, Western; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D005938:Glucocorticoids / Q000378:metabolism*; D007700:Kinetics; D008223:Lymphoma / Q000473:pathology; D051379:Mice; D009154:Mutation; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013953:Thymus Neoplasms / Q000473:pathology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D016376:Oligonucleotides, Antisense; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014157:Transcription Factors; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C055473:enhancer-binding protein AP-4; D005047:Etoposide; D003907:Dexamethasone; C506434:Casp9 protein, mouse; D053453:Caspase 9; D020169:Caspases