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The binding of a Fos/Jun heterodimer can completely disrupt the structure of a nucleosome

K W Ng1, P Ridgway, D R Cohen

  • 1Division of Biochemistry, The John Curtin School of Medical Research, The Australian National University, Canberra.

The EMBO Journal
|April 15, 1997
PubMed

Insights

The Fos/Jun transcriptional activator binds differently to acetylated and unacetylated nucleosomes. Acetylated nucleosomes disrupt their structure upon Fos/Jun binding, enabling further transcription factor access.

Area of Science:

  • Molecular Biology
  • Epigenetics
  • Gene Regulation

Background:

  • Chromatin remodeling is crucial for gene regulation.
  • Transcriptional activators initiate gene expression by binding DNA.
  • Nucleosomes, DNA wrapped around histones, pose a barrier to transcription factor binding.

Purpose of the Study:

  • To investigate the interaction of Fos/Jun with its binding site within a nucleosomal template.
  • To determine how nucleosome acetylation affects Fos/Jun binding affinity and nucleosome structure.
  • To assess the impact of Fos/Jun binding on subsequent transcription factor accessibility.

Main Methods:

  • Reconstitution of nucleosomes with acetylated and non-acetylated histone variants.
  • Electrophoretic mobility shift assays (EMSAs) to assess DNA binding.
  • Analysis of nucleosome structural integrity upon transcription factor binding.

Main Results:

  • Fos/Jun binding affinity to unacetylated nucleosomes was reduced only 4-5 fold compared to naked DNA.
  • Binding of Fos/Jun to acetylated nucleosomes caused complete disruption of the nucleosome structure.
  • Histone displacement was not observed during nucleosome disruption.
  • Nucleosome disruption by Fos/Jun facilitated the binding of a second transcription factor.

Conclusions:

  • Nucleosome acetylation status significantly modulates the interaction of Fos/Jun with its DNA binding site.
  • Acetylated nucleosomes are more susceptible to disruption by Fos/Jun, leading to altered chromatin structure.
  • This disruption mechanism may play a role in facilitating the assembly of transcription initiation complexes.

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