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A phospho-dependent mechanism involving NCoR and KMT2D controls a permissive chromatin state at Notch target genes

Franz Oswald1, Patrick Rodriguez2, Benedetto Daniele Giaimo3

  • 1University Medical Center Ulm, Center for Internal Medicine, Department of Internal Medicine I, Albert-Einstein-Allee 23, 89081 Ulm, Germany franz.oswald@uni-ulm.de.

Nucleic Acids Research
|February 26, 2016
PubMed

Insights

Notch gene activation relies on switching from repressive to active chromatin marks. SHARP protein balances these states by interacting with repressors (NCoR) and activators (KMT2D), controlled by NCoR phosphorylation.

Area of Science:

  • Molecular Biology
  • Epigenetics
  • Developmental Biology

Background:

  • Notch signaling controls gene expression through dynamic chromatin changes.
  • Histone H3 lysine-4 (H3K4) demethylases establish repressive chromatin states at Notch target genes.
  • The histone methyltransferase counteracting this process remained unidentified.

Purpose of the Study:

  • To identify the histone methyltransferase involved in Notch target gene activation.
  • To elucidate the mechanism by which chromatin states are switched for Notch responses.
  • To investigate the role of SHARP protein in coordinating these chromatin modifications.

Main Methods:

  • Co-immunoprecipitation assays to study protein interactions.
  • Site-directed mutagenesis to investigate phosphorylation effects.
  • In vivo studies using Drosophila homologs of SHARP and KMT2D.
  • Biochemical assays to analyze protein complex formation.

Main Results:

  • SHARP interacts with both the NCoR corepressor and the KMT2D histone methyltransferase complex.
  • KMT2D and NCoR compete for binding to SHARP's SPOC-domain.
  • Phosphorylation of NCoR dictates its binding to SHARP, influencing the balance between repression and activation.
  • SHARP and KMT2D homologs in Drosophila regulate Notch-mediated functions.

Conclusions:

  • Signaling-mediated phosphorylation of NCoR fine-tunes SHARP's interaction with KMT2D, thereby controlling chromatin states.
  • This mechanism reveals how phosphorylation regulates the switch between gene repression and activation in Notch signaling.
  • The findings highlight a conserved mechanism for chromatin-based control of developmental signaling pathways.

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