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Nuclear accumulation of cRel following C-terminal phosphorylation by TBK1/IKK epsilon

Jennifer Harris1, Stéphanie Olière, Sonia Sharma

  • 1Terry Fox Molecular Oncology Group, Lady Davis Institute for Medical Research, 3755 chemin de la Cote Sainte Catherine, Montréal, Québec, Canada.

Journal of Immunology (Baltimore, Md. : 1950)
|August 5, 2006
PubMed

Insights

New research reveals that IKKepsilon and TBK1 directly phosphorylate cRel, a key transcription factor. This phosphorylation regulates nuclear accumulation of cRel independently of the classical pathway, uncovering a novel mechanism for NF-kappaB regulation.

Area of Science:

  • Molecular Biology
  • Immunology
  • Cell Signaling

Background:

  • Nuclear Factor-kappaB (NF-kappaB) transcription factors regulate critical cellular processes.
  • NF-kappaB activity is primarily controlled by the IkappaB kinase (IKK) complex, involving IkappaB phosphorylation and degradation.
  • The roles of IKK-related kinases TBK1 and IKKepsilon in NF-kappaB regulation are not fully understood.

Purpose of the Study:

  • To investigate whether IKKepsilon and TBK1 modulate the activity of the NF-kappaB subunit cRel through phosphorylation.
  • To elucidate the mechanism by which TBK1 and IKKepsilon influence cRel activity.

Main Methods:

  • In vitro and in vivo phosphorylation assays using TBK1 and IKKepsilon.
  • Analysis of cRel nuclear accumulation.
  • Assessment of IkappaBalpha degradation and IkappaBalpha-cRel complex stability.

Main Results:

  • TBK1 and IKKepsilon directly phosphorylate the C-terminal domain of cRel.
  • This phosphorylation regulates the nuclear accumulation of cRel independently of the canonical IkappaB/IKK pathway.
  • IKKepsilon-mediated phosphorylation of cRel promotes the dissociation of the IkappaBalpha-cRel complex without affecting IkappaBalpha degradation.

Conclusions:

  • IKKepsilon and TBK1 directly phosphorylate cRel, representing a novel regulatory mechanism for this transcription factor.
  • This phosphorylation event controls cRel's nuclear localization and function outside the classical IkappaB degradation pathway.
  • These findings reveal a previously unrecognized pathway for NF-kappaB regulation via direct phosphorylation of cRel by IKKepsilon and TBK1.

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