Activation of NF-kappa B is one of the earliest responses at the start of liver regeneration, and is required for hepatocyte cell cycle progression. The A20-binding inhibitor of NF-kappa B activation-2, ABIN-2, is an inhibitor of NF-kappa B. However, its effects on hepatocyte cell cycle progression are not known and its involvement in liver regeneration has not been explored. In this study, the temporal expression pattern of the mouse ABIN-2 was studied during liver regeneration induced by partial hepatectomy. We demonstrate that ABIN-2 is rapidly and transiently induced, and expression peaked at around 8 h post-hepatectomy. To test that the inducible expression of ABIN-2 serves to regulate NF-kappa B during liver regeneration, transgenic mice overexpressing human ABIN-2 protein in the liver were generated. Our transgenic data demonstrated that overexpression of ABIN-2 inhibited NF-kappa B nuclear translocation, which peaked at around 2-4 h post-hepatectomy, and this led to an impairment of the G1/S transition as well as a delay in hepatocyte cell cycle progression of the regenerating liver. In addition, overexpression of ABIN-2 specifically inhibited endogenous ABIN-2 mRNA induction, suggesting a negative feedback mechanism for ABIN-2 expression. In conclusion, ABIN-2 may function as a negative regulator that downregulates NF-kappa B activation during liver regeneration. (c) 2006 Elsevier Inc. All rights reserved.