Gene Expression Profiling in Conjunction with Physiological Rescues of IKKα-null Cells with Wild Type or Mutant IKKα Reveals Distinct Classes of IKKα/NF-κB-dependent Genes

Cellular responses to stress-like stimuli require the IκB kinase (IKK) signalsome (IKKα, IKKβ, and NEMO/IKKγ) to activate NF-κB-dependent genes. IKKβ and NEMO/IKKγ are required to release NF-κB p65/p50 heterodimers from IκBα, resulting in their nuclear migration and sequence-specific DNA binding; bu...

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Bibliographic Details
Published in:The Journal of biological chemistry 2005-04, Vol.280 (14), p.14057-14069
Main Authors: Massa, Paul E., Li, Xiang, Hanidu, Adedayo, Siamas, John, Pariali, Milena, Pareja, Jessica, Savitt, Anne G., Catron, Katrina M., Li, Jun, Marcu, Kenneth B.
Format: Article
Language:English
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Summary:Cellular responses to stress-like stimuli require the IκB kinase (IKK) signalsome (IKKα, IKKβ, and NEMO/IKKγ) to activate NF-κB-dependent genes. IKKβ and NEMO/IKKγ are required to release NF-κB p65/p50 heterodimers from IκBα, resulting in their nuclear migration and sequence-specific DNA binding; but IKKα was found to be dispensable for this initial phase of canonical NF-κB activation. Nevertheless, IKKα(-/-) mouse embryonic fibroblasts (MEFs) fail to express NF-κB targets in response to proinflammatory stimuli, uncovering a nuclear role for IKKα in NF-κB activation. However, it remains unknown whether the global defect in NF-κB-dependent gene expression of IKKα(-/-) cells is caused by the absence of IKKα kinase activity. We show by gene expression profiling that rescue of near physiological levels of wild type IKKα in IKKα(-/-) MEFs globally restores expression of their canonical NF-κB target genes. To prove that the kinase activity of IKKα was required on a genomic scale, the same physiological rescue was performed with a kinase-dead, ATP binding domain IKKα mutant (IKKα(K44M)). Remarkably, the IKKα(K44M) protein rescued ∼28% of these genes, albeit in a largely stimulus-independent manner with the notable exception of several genes that also acquired tumor necrosis factor-α responsiveness. Thus the IKKα-containing signalsome unexpectedly functions in the presence and absence of extracellular signals in both kinase-dependent and -independent modes to differentially modulate the expression of five distinct classes of IKKα/NF-κB-dependent genes.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M414401200