Cryo-EM structures of the XPF-ERCC1 endonuclease reveal how DNA-junction engagement disrupts an auto-inhibited...

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The XPF-ERCC1 complex is essential for DNA repair pathways like nucleotide excision repair (NER) and inter-strand crosslink repair (ICLR).
• The mechanism of catalytic activation of XPF-ERCC1 by DNA junction substrates remains unclear.

Purpose of the Study:

• To elucidate the structural basis of XPF-ERCC1 auto-inhibition and activation by DNA substrates.
• To investigate the impact of patient-derived mutations on XPF-ERCC1 structure and function.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structures of DNA-free and DNA-bound human XPF-ERCC1.
• Structure-function analyses were performed using patient mutations.

Main Results:

• The DNA-free XPF-ERCC1 adopts an auto-inhibited conformation, with the XPF helical domain blocking the ERCC1 (HhH)2 domain and catalytic site.
• DNA junction binding induces a conformational change, releasing the ERCC1 (HhH)2 domain to interact with nuclease domains.
• Mutations found in xeroderma pigmentosum patients often disrupt the structural integrity of XPF-ERCC1.
• Mutations in Fanconi anemia patients can lead to enzymes with high in vitro activity but impaired activation by SLX4.

Conclusions:

• The study provides novel insights into the architecture of XPF-ERCC1 and its mechanism of catalytic activation.
• Understanding these structural and functional aspects is crucial for comprehending DNA repair deficiencies and developing therapeutic strategies.