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Author Spotlight: Quantitative Detection of DNA Protein Crosslinks and Their Post-Translational Modifications
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Author Spotlight: Quantitative Detection of DNA Protein Crosslinks and Their Post-Translational Modifications

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The DNA-damage kinase ATR activates the FANCD2-FANCI clamp by priming it for ubiquitination

Tamara Sijacki1, Pablo Alcón1, Zhuo A Chen2

  • 1MRC Laboratory of Molecular Biology, Cambridge, UK.

Nature Structural & Molecular Biology
|September 1, 2022
PubMed

Insights

DNA interstrand cross-links trigger ATR kinase to phosphorylate FANCI, priming the FANCD2-FANCI DNA repair clamp for ubiquitination. This phosphorylation controls DNA repair coordination, crucial for preventing tumor formation.

Area of Science:

  • Molecular Biology
  • DNA Repair Mechanisms
  • Cancer Biology

Background:

  • DNA interstrand cross-links are genotoxic lesions that impede DNA replication and transcription.
  • The Fanconi anemia pathway, involving ATR kinase, FANCI, and FANCD2, is critical for repairing these cross-links.
  • The precise mechanism by which phosphorylation activates this DNA repair pathway remained unclear.

Purpose of the Study:

  • To elucidate the structural and functional consequences of FANCI phosphorylation in the DNA repair process.
  • To understand how phosphorylation primes the FANCD2-FANCI complex for subsequent ubiquitination and DNA repair.

Main Methods:

  • X-ray crystallography to determine the structures of FANCD2-FANCI complexes with phosphomimetic FANCI.
  • Biophysical analyses to assess DNA binding and conformational dynamics of the complexes.

Main Results:

  • Phosphomimetic mutations in FANCI cause the FANCD2-FANCI complex to adopt a closed conformation around DNA, independent of the Fanconi anemia core complex.
  • These mutations destabilize the open state of FANCD2-FANCI and alter its conformational dynamics without significantly affecting DNA binding.
  • Phosphorylation acts as a priming step, preparing the FANCD2-FANCI clamp for ubiquitination.

Conclusions:

  • Phosphorylation of FANCI is a key regulatory event that primes the FANCD2-FANCI complex for ubiquitination.
  • This study reveals the coordinated action of posttranslational modifications in controlling DNA repair pathways.
  • Understanding this mechanism provides insights into preventing DNA cross-link-induced tumorigenesis.

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