Nuclear Factor-kappa B (NF-kappa B) is a transcription factor essential to the control of cell proliferation, survival, differentiation, immune response, and inflammation. Constitutive NF-kappa B activation has been observed in a broad variety of solid tumors and hematological malignancies, which suggests that NF kappa B signaling may perform a critical role in the development of human cancers. Interferon regulatory factor-2 (IRF-2), an antagonistic transcriptional repressor of IRF-1, evidences oncogenic potential, but little is currently known regarding the mechanism underlying the oncogenic activities of IRF-2. In this study, we report that IRF-2 recruits RelA/p65 transcription factors into the nucleus via physical interaction. While the nuclear recruitment of RelA by IRF-2 augments TNF alpha-induced NF-kappa B dependent transcription, the N-terminal truncated mutant form of IRF-2 inhibits the nuclear localization of RelA, and thus interferes with NF-kappa B activation. Furthermore, the knockdown of IRF-2 by IRF-2 siRNA attenuates TNFa-induced NF-kappa B dependent transcription by inhibiting the nuclear localization of RelA. Thus, these results show that IRF-2 regulates NF-kappa B activity via the modulation of NF-KB subcellular localization. (c) 2008 Elsevier Inc. All rights reserved.