Evidence that de novo protein synthesis is dispensable for anti-apoptotic effects of NF-κB

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Abstract
The transcription factor NF-κB is a positive transcription factor for a number of genes and has been recognized as an anti-apoptotic regulator. However, the mechanism by which NF-κB blocks apoptosis is still controversial. Here, we demonstrate the evidence that NF-κB could attenuate the TNF-α-induced apoptosis without de novo protein synthesis using human pancreatic cancer cell lines, MIA PaCa-2 and Capan-2. The TNF-α-induced apoptosis was blocked by IL-1β, a potent inducer of NF-κB activation. This inhibitory effect of IL-1β was evident when cells were treated with protein synthesis inhibitors such as cycloheximide (CHX). Moreover, NF-κB decoy oligonucleotides could not block the anti-apoptotic effect of IL-1β at doses sufficient to block the NF-κB-dependent transcription induced by IL-1β. To confirm the role of NF-κB in blocking apoptosis, we generated stable cell lines expressing IκBΔN, a highly stable form of IκBα, a cytoplasmic inhibitor of NF-κB. In these stable transfectants, the anti-apoptotic effect of IL-1β was totally abolished, indicating that the anti-apoptotic action of IL-1β could be ascribed to the NF-κB action. These findings show that de novo protein synthesis is dispensable for anti-apoptotic effects of NF-κB and support the possibility that NF-κB could exert its anti-apoptotic action through protein-protein interaction.