This study reveals a new complexity in the cellular response to DNA damage: activation of interferon (IFN) signaling. The DNA damage response involves the rapid recruitment of repair enzymes, and the activation of signal transducers that regulate cell cycle checkpoints and cell survival. To understand the link between DNA damage and innate cellular defense that occurs in response to many viral infections, we evaluated the effects of agents such as etoposide that promote double-stranded DNA breaks. Treatment of human cells with etoposide led to the induction of IFN-stimulated genes, and the IFN-α and IFN-λ genes. The nuclear factor-κB (NF-κB), known to be activated in response to DNA damage, was shown to be a key regulator of this IFN gene induction. Expression of an NF-κB subunit, p65/RelA was sufficient for induction of the human IFN-λ1 gene. In addition, NF-κB was required for the induction of the IFN regulatory factors-1 and -7 that are able to stimulate expression of the IFN-α and IFN-λ genes. Cells that lack the NF-κB essential modulator (NEMO), lack the ability to induce the IFN genes following DNA damage. Breaks in DNA are generated during normal physiological processes of replication, transcription, and recombination, as well as by external genotoxic agents or infectious agents. The significant finding of IFN production as a stress response to DNA damage provides a new perspective on the role of IFN signaling.

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