Inducible phosphorylation of I kappa B alpha is not sufficient for its dissociation from NF-kappa B and is inhibited by protease inhibitors.
The ubiquitous transcription factor NF-kappa B is regulated by its cytoplasmic inhibitor I kappa B. A variety of cellular stimuli cause the dissociation of NF-kappa B from I kappa B, allowing NF-kappa B to translocate to the nucleus and regulate gene expression. Although the activation of NF-kappa B in vivo is associated with the phosphorylation and degradation of I kappa B alpha, it has remained unclear how each of these events contributes to this process. Recently, studies utilizing protease inhibitors have suggested that the proteolysis of I kappa B alpha is a necessary event in the activation of NF-kappa B. We demonstrate in this study that these and an additional protease inhibitor also completely repress inducible phosphorylation of I kappa B alpha. This surprising result suggests a more complex role of proteases in NF-kappa B activation. In addition, data presented here indicate that many of these inhibitors also directly modify NF-kappa B and inhibit its DNA binding activity. Due to the pleiotropic effects of these protease inhibitors, it is difficult to conclude from their use how I kappa B alpha phosphorylation and degradation contribute to NF-kappa B activation. In the present study, a more direct approach demonstrates that phosphorylation of I kappa B alpha alone is not sufficient for NF-kappa B activation.
Finco
T S
TS
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599.
Beg
A A
AA
Baldwin
A S
AS
D001483:Base Sequence; D004273:DNA, Neoplasm / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015345:Oligonucleotide Probes; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology*; D011485:Protein Binding; D013601:T-Lymphocytes; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D015345:Oligonucleotide Probes; D011480:Protease Inhibitors; D000072000:NF-KappaB Inhibitor alpha