Nuclear factor kappa B (NF-kappa B) is a transcription factor that is
critical for the inducible expression of multiple cellular and viral g
enes. Using the electrophoretic mobility shift assay, we demonstrated
that DNA binding activity of NF-kappa B was abolished by proteolysis w
ith mu- and m-calpains in vitro. The proteolysis of NF-kappa B by calp
ains and hence the abolition of its DNA binding was prevented by calpa
statin, 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 o
bservations indicate that calpains regulate gene expression through pr
ocessing of NF-kappa B.