Establishment of a newly improved detection system for NF-kappaB activity.

The transcription factor nuclear factor-kappaB (NF-kappaB) plays roles in apoptosis, inflammation and oncogenesis. It is important for biological and medical research to understand when proteins of interest are activated in cells, leading to the establishment of a luciferase/EGFP assay to monitor the activation of transcription factors. Here, we describe an improved reporter system for NF-kappaB, the NF-kappaB-activated transgene (NAT) system that can detect NF-kappaB signalling with high sensitivity and specificity. The NAT system consists of large copy numbers of NF-kappaB consensus sequence and a minimal promoter derived from the mouse interleukin-2 (IL-2) gene. Furthermore, we generated NAT systems with stable or unstable luciferase/EGFP proteins. Stable and unstable types of luciferase/EGFP are suitable for analyzing the accumulation of and the real-time activity of NF-kappaB signal, respectively. Our findings suggest that the NAT system is effective for in vivo imaging of NF-kappaB signalling using cells or animals.