DNA-Dependent Protein Kinase Phosphorylation of IκBα and IκBβ Regulates NF-κB DNA Binding Properties release_lup3k6thojdsfmqtrdnyveo65a

by Li Liu, Youn-Tae Kwak, Françoise Bex, León F. García-Martínez, Xiao-Hua Li, Katheryn Meek, William S. Lane, Richard B. Gaynor

Published in Molecular and Cellular Biology by American Society for Microbiology.

1998   Volume 18, p4221-4234

Abstract

Regulation of the IκBα and IκBβ proteins is critical for modulating NF-κB-directed gene expression. Both IκBα and IκBβ are substrates for cellular kinases that phosphorylate the amino and carboxy termini of these proteins and regulate their function. In this study, we utilized a biochemical fractionation scheme to purify a kinase activity which phosphorylates residues in the amino and carboxy termini of both IκBα and IκBβ. Peptide microsequence analysis by capillary high-performance liquid chromatography ion trap mass spectroscopy revealed that this kinase was the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). DNA-PK phosphorylates serine residue 36 but not serine residue 32 in the amino terminus of IκBα and also phosphorylates threonine residue 273 in the carboxy terminus of this protein. To determine the biological relevance of DNA-PK phosphorylation of IκBα, murine severe combined immunodeficiency (SCID) cell lines which lack the DNA-PKcs gene were analyzed. Gel retardation analysis using extract prepared from these cells demonstrated constitutive nuclear NF-κB DNA binding activity, which was not detected in extracts prepared from SCID cells complemented with the human DNA-PKcs gene. Furthermore, IκBα that was phosphorylated by DNA-PK was a more potent inhibitor of NF-κB binding than nonphosphorylated IκBα. These results suggest that DNA-PK phosphorylation of IκBα increases its interaction with NF-κB to reduce NF-κB DNA binding properties.
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Type  article-journal
Stage   published
Date   1998-07-01
Language   en ?
DOI  10.1128/mcb.18.7.4221
PubMed  9632806
PMC  PMC109006
Wikidata  Q24522560
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