Inhibition of the NF-kappa B transcription factor increases Bax expression in cancer cell lines.
The NF-kappa B transcription factor has been shown to inhibit apoptosis in several experimental systems. We therefore investigated whether the expression of the Bax proapoptotic protein could be influenced by NF-kappa B activity. Increased Bax protein expression was detected in HCT116, OVCAR-3 and MCF7 cells stably expressing a mutated unresponsive I kappa B-alpha inhibitory protein that blocks NF-kappa B activity. Northern blots showed that bax mRNA expression was increased as a consequence of mutated I kappa B-alpha expression in HCT116 cells. A careful examination of the human bax gene promoter sequence showed three putative binding sites for NF-kappa B, and the kappa B2 site at position -687 could indeed bind NF-kappa B complexes in vitro. Transient transfection of a bax promoter luciferase construct in HCT116 cells showed that NF-kappa B proteins could partially inhibit the transactivation of the bax promoter by p53. Mutations or deletions of the kappa B sites, including kappa B2, indicated that this NF-kappa B-dependent inhibitory effect did not require NF-kappa B DNA-binding, and was thus an indirect effect. However, cotransfection of expression vectors for several known cofactors failed to identify a competition between p53 and NF-kappa B for a transcription coactivator. Our findings thus demonstrate for the first time that NF-kappa B regulates, through an indirect pathway, the bax gene expression.
Bentires-Alj
M
M
Laboratory of Medical Chemistry and Medical Oncology, University of Liège, Belgium.
Dejardin
E
E
Viatour
P
P
Van Lint
C
C
Froesch
B
B
Reed
J C
JC
Merville
M P
MP
Bours
V
V
D001665:Binding Sites; D004273:DNA, Neoplasm / Q000378:metabolism*; D017930:Genes, Reporter; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D009154:Mutation; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D004273:DNA, Neoplasm; D016328:NF-kappa B; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein