Enhanced I kappa B alpha degradation is responsible for constitutive NF-kappa B activity in mature murine B-cell lines.
Nuclear factor kappa B (NF-kappa B) is a ubiquitous transcription factor which binds to decameric DNA sequences (kappa B sites) and regulates transcription of multiple genes. The activity of NF-kappa B is regulated by an inhibitor protein, I kappa B, which sequesters NF-kappa B in the cytoplasm. Release of I kappa B and subsequent nuclear translocation of NF-kappa B generally require activating signals. However, in mature murine B cells, the DNA-binding activity of NF-kappa B is constitutively nuclear and activates the Ig kappa gene, a marker for mature B cells. To understand the basis for the constitutive NF-kappa B activation, we examined the properties of NF-kappa B and I kappa B in both pre-B and mature B cells, the regulated and constitutive states, respectively. We found that expression of I kappa B alpha and p105, members of the I kappa B family, and Rel, a member of the NF-kappa B family, is augmented in mature B cells. Both I kappa B alpha and p 105 are associated with NF-kappa B proteins and sequester most of these proteins in the cytoplasm of mature B cells. However, rapid I kappa B alpha dissociation and degradation lead to continuous nuclear translocation of a small fraction of NF-kappa B proteins, which represent the constitutively active NF-kappa B in mature B cells. We estimate that the protease activity is at least 35-fold greater in mature B cells than in pre-B cells. Rapid degradation of I kappa B alpha is directly involved in constitutive NF-kappa B activation, because stabilization of I kappa B alpha by a protease inhibitor causes loss of NF-kappa B activity in mature B cells. These results provide evidence that continuous and rapid degradation of I kappa B alpha in the absence pf external stimuli is causally involved in the constitutive activation of NF-kappa B in mature murine B cells.
Miyamoto
S
S
Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92186-5800.
Chiao
P J
PJ
Verma
I M
IM
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D005803:Genes, Immunoglobulin; D020672:I-kappa B Proteins; D007106:Immune Sera; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis / Q000235:genetics*; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D015183:Restriction Mapping; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D007106:Immune Sera; D007145:Immunoglobulin kappa-Chains; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D009838:Oligodeoxyribonucleotides; D010455:Peptides; D000072000:NF-KappaB Inhibitor alpha; D014108:Tosylphenylalanyl Chloromethyl Ketone