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RSK-mediated phosphorylation in the C/EBP{beta} leucine zipper regulates DNA binding, dimerization, and growth arrest

Sook Lee1, Jon D Shuman, Tad Guszczynski

  • 1Laboratory of Cancer Prevention, Bldg. 539 Room 122, NCI-Frederick, Frederick, MD 21702-1201, USA.

Molecular and Cellular Biology
|March 31, 2010
PubMed

Insights

Ras signaling activates the C/EBPbeta transcription factor through four novel modifications, including RSK-mediated phosphorylation. This process is crucial for DNA binding, homodimerization, and promoting cell cycle arrest in cancer.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • C/EBPbeta, a bZIP transcription factor, is a key player in Ras signaling pathways.
  • Ras-induced transformation and oncogene-induced senescence (OIS) involve C/EBPbeta.
  • Understanding C/EBPbeta activation by oncogenic Ras is crucial for cancer research.

Purpose of the Study:

  • To investigate the mechanisms of C/EBPbeta activation by oncogenic Ras.
  • To identify novel modifications regulating C/EBPbeta activity and function.
  • To elucidate the role of C/EBPbeta in Ras-mediated cellular processes.

Main Methods:

  • Investigated C/EBPbeta activation using oncogenic Ras signaling models.
  • Utilized biochemical assays to study C/EBPbeta DNA binding and modifications.
  • Employed site-directed mutagenesis to analyze the function of specific residues.

Main Results:

  • Ras-Raf-MEK-ERK-p90(RSK) cascade activates C/EBPbeta DNA binding.
  • RSK-mediated phosphorylation of Ser273 is essential for DNA binding and homodimerization.
  • Three additional modifications (p-Tyr109, p-Ser111, me-Arg114) in the N-terminal domain regulate activation and cytostatic activity.

Conclusions:

  • Identified four novel C/EBPbeta-activating modifications, including RSK-mediated phosphorylation.
  • Ser273 phosphorylation regulates both DNA binding and homodimerization, promoting cell cycle arrest.
  • These findings provide insights into Ras-C/EBPbeta signaling in cellular transformation and senescence.

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