Negative regulation of protein phosphatase 2Cβ by ISG15 conjugation

ISG15, an interferon-upregulated ubiquitin-like protein, is covalently conjugated to various cellular proteins (ISGylation). In this study, we found that protein phosphatase 2C beta (PP2C beta), which functions in the nuclear factor kappa B (NF-kappa B) pathway via dephosphorylation of TGF-beta-activated kinase, was ISGylated, and analysis by NF-kappa B luciferase reporter assay revealed that PP2C beta activity was suppressed by co-expression of ISG15, UBE1L, and UbcH8. We determined the ISGylation sites of PP2CP and constructed its ISGylation-resistant mutant. In contrast to the wild type, this mutant suppressed the NF-kappa B pathway even in the presence of ISG15, UBE1L, and UbcH8. Thus, we propose that ISGylation negatively regulates PP2CP activity. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.