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Architecture and DNA recognition elements of the Fanconi anemia FANCM-FAAP24 complex

Rachel Coulthard1, Andrew J Deans, Paolo Swuec

  • 1Structural Biology Laboratory, Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.

Structure (London, England : 1993)
|August 13, 2013
PubMed

Insights

Fanconi anemia (FA) protein FANCM and its partner FAAP24 are crucial for DNA repair. Structural and functional studies reveal how they bind DNA and remodel stalled replication forks, offering insights into FA disease mechanisms.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Fanconi anemia (FA) is a rare genetic disorder characterized by bone marrow failure and increased cancer risk due to defects in DNA repair pathways.
  • The FANCM-FAAP24 complex plays a critical role in the FA pathway by targeting other FA proteins to sites of DNA damage.

Purpose of the Study:

  • To elucidate the structural and functional mechanisms of the FANCM-FAAP24 complex in DNA repair.
  • To investigate the interaction of FANCM-FAAP24 with DNA and its role in replication fork remodeling.

Main Methods:

  • X-ray crystallography to determine the structure of the FANCM C-terminal domain (FANCMCTD) bound to FAAP24 and DNA.
  • Site-directed mutagenesis to assess the impact of specific mutations on DNA binding and protein function.
  • Electron microscopy to analyze the proximity of the FANCM translocase domain to FANCMCTD.
  • In vitro assays to measure double-stranded DNA binding and ATPase activity.

Main Results:

  • The crystal structure revealed an S-shaped complex with the FAAP24 (HhH)2 domain engaging DNA, while the FANCM (HhH)2 domain is buried.
  • A second DNA contact site and a metal center within the FANCM pseudo-nuclease domain were identified.
  • Mutations in these regions impaired in vitro DNA binding and in vivo FANCM-FAAP24 function.
  • Electron microscopy showed the FANCM translocase domain near FANCMCTD, and binding to fork DNA structures stimulated its ATPase activity.

Conclusions:

  • The FANCM-FAAP24 complex utilizes distinct domains for DNA binding and ATPase-dependent remodeling of stalled replication forks.
  • A proposed model suggests FANCM-FAAP24 tracks DNA until it encounters a stalled fork, triggering remodeling.
  • These findings provide critical insights into the molecular mechanisms underlying Fanconi anemia and DNA repair.

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