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E2F1 binds to the peptide-binding groove within the BIR3 domain of cIAP1 and requires cIAP1 for chromatin binding

Jennifer Allègre1,2, Jessy Cartier1,2, Valérie Glorian1,2

  • 1Institut National de la Santé et de la Recherche Médicale (Inserm), LNC UMR1231, Dijon, France.

Plos One
|October 26, 2018
PubMed

Insights

Cellular inhibitor of apoptosis 1 (cIAP1) regulates cell fate by binding to the E2F1 transcription factor via its BIR3 domain. This interaction influences E2F1 ubiquitination and chromatin recruitment, suggesting a regulatory feedback loop.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Cellular inhibitor of apoptosis 1 (cIAP1) is an E3-ubiquitin ligase crucial for regulating cell signaling pathways.
  • cIAP1 controls fundamental cellular processes, including cell death, proliferation, differentiation, and inflammation.
  • Previous work established cIAP1's role in promoting E2F1 ubiquitination and stabilization during S phase and DNA damage responses.

Purpose of the Study:

  • To elucidate the specific binding interaction between cIAP1 and the E2F1 transcription factor.
  • To investigate the functional consequences of cIAP1-E2F1 interaction on E2F1 ubiquitination and chromatin association.
  • To explore potential auto-regulatory mechanisms involving cIAP1 and E2F1.

Main Methods:

  • Protein-protein interaction studies to map binding sites.
  • Use of Smac peptides and mimetics to probe the cIAP1 binding pocket.
  • Analysis of E2F1 ubiquitination profiles using specific ubiquitin linkage chain antibodies.
  • Chromatin immunoprecipitation sequencing (ChIP-seq) to assess E2F1 recruitment to chromatin.
  • Promoter analysis to identify potential regulatory elements.

Main Results:

  • E2F1 binds to the BIR3 domain of cIAP1, specifically interacting with a surface hydrophobic groove that accommodates the IAP binding motif (IBM).
  • The first alpha-helix of the BIR3 domain is essential for E2F1, Smac, and Smac mimetic binding.
  • cIAP1 overexpression alters E2F1 ubiquitination, favoring K11- and K63-linked chains while reducing K48-linked chains.
  • cIAP1 is essential for E2F1 recruitment onto chromatin, as shown by ChIP-seq.
  • An E2F-binding site was identified on the promoter of the cIAP1-encoding birc2 gene.

Conclusions:

  • The BIR3 domain of cIAP1, particularly its hydrophobic groove and first alpha-helix, mediates the interaction with E2F1.
  • cIAP1 modulates E2F1 ubiquitination status, impacting its stability and function.
  • cIAP1 is critical for E2F1's chromatin association, influencing gene regulation.
  • A novel auto-regulatory feedback loop is proposed where E2F1 regulates cIAP1 expression.

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