Abstract LB-235: SUMO-1 modification represses CPAP transcriptional co-activator activity in TNFα-induced NF-κB signaling pathway

Abstract The transcription factor nuclear factor-κB (NF-κB) is an important regulator in inflammation, immune responses, apoptosis, cell proliferation and differentiation. CPAP (Centrosomal protein P4.1-associated protein), which plays important roles on centrosomal functions, is previously identified as the transcriptional coactivator for NF-κB. Here, we have demonstrated that decreased expression of CPAP by siRNA can attenuate NF-κB-mediated genes expression under TNFα stimulus. On the contrary, overexpressed CPAP contributes to the NF-κB-driven transcriptional activation. Immunoflourescence data showed that the nuclear localization of CPAP is induced by TNFα stimulus. Chromatin immunoprecipitation assay further indicated that CPAP was recruited to COX-2 promoter region under TNF treatment. We found that the NF-κB signaling pathway is activated by CPAP through recruiting more IKKß to the inactivated NF-κB complex to enhance the degradation of IκB and the phosphorylation of p65. Importantly, CPAP was covalently modified by small ubiquitin-related modifier-1 (SUMO-1) protein under TNFα stimulus, and the specific acceptor sites were located in the C-terminal of CPAP. Interestingly, when overexpressing SUMO-deficient CPAP in A549 cells, the TNFα-induced NF-κB-mediated genes expression was up-regulated. Co-immunoprecipitation assay showed that the association of IKKß to NF-κB complex was augmented by SUMO-deficient CPAP than wild type CPAP. Taken together, these results suggest that there might be a mechanism for the SUMOylation of CPAP in modulating the activity of NF-κB. The detailed machinery for SUMOylated CPAP in the TNFα-induced NF-κB activation is currently under investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-235.