Constitutive phosphorylation of I kappa B alpha by casein kinase II.
The NF-kappa B/Rel proteins are sequestered in the cytoplasm in association with the phosphorylated form of I kappa B alpha. Upon induction with a wide variety of agents, the activity of NF-kappa B/Rel proteins is preceded by the rapid degradation of I kappa B alpha protein. We report the identification and partial purification of a cellular kinase from unstimulated or stimulated murine cells, which specifically phosphorylates the C terminus of I kappa B alpha. There are several consensus sites for casein kinase II (CKII) in the C-terminal region of I kappa B alpha. Additionally, the activity of the cellular kinase is blocked by antibodies against the alpha subunit of CKII. No phosphorylation of the C-terminal region of I kappa B alpha can be detected if the five possible serine and threonine residues that can be phosphorylated by CKII are mutated to alanine. A two-dimensional tryptic phosphopeptide map of I kappa B alpha from unstimulated cells was identical to that obtained by in vitro phosphorylation of I kappa B alpha with the partially purified cellular kinase. We propose that constitutive phosphorylation of I kappa B alpha is carried out by CKII.
Barroga
C F
CF
Molecular Biology and Virology Laboratory, Salk Institute, San Diego, CA 92186-5800, USA.
Stevenson
J K
JK
Schwarz
E M
EM
Verma
I M
IM
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001402:B-Lymphocytes; D047390:Casein Kinase II; D002460:Cell Line; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli; D005982:Glutathione Transferase / Q000378:metabolism; D020672:I-kappa B Proteins; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D017384:Sequence Deletion; D013379:Substrate Specificity
D000906:Antibodies; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D046911:Macromolecular Substances; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D011993:Recombinant Fusion Proteins; D000072000:NF-KappaB Inhibitor alpha; D005982:Glutathione Transferase; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases