Proteolytic processing of nuclear factor kappa B by calpain in vitro

Nuclear factor kappa B (NF-kappa B) is a transcription factor that is critical for the inducible expression of multiple cellular and viral genes. Using the electrophoretic mobility shift assay, we demonstrated that DNA binding activity of NF-kappa B was abolished by proteolysis with mu- and m-calpains in vitro. The proteolysis of NF-kappa B by calpains and hence the abolition of its DNA binding was prevented by calpastatin, calpain inhibitor I and proteasome inhibitor. We also provided evidence that calpains degrade the C-terminal domain of NF-kappa B by Western blot using anti-NF-kappa B (p65) C-terminal antibody. These observations indicate that calpains regulate gene expression through processing of NF-kappa B.