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Characterizing DNA Repair Processes at Transient and Long-lasting Double-strand DNA Breaks by Immunofluorescence Microscopy
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Tandem protein interaction modules organize the ubiquitin-dependent response to DNA double-strand breaks

Stephanie Panier1, Yosuke Ichijima, Amélie Fradet-Turcotte

  • 1Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada.

Molecular Cell
|June 30, 2012
PubMed

Insights

Researchers discovered that specific protein modules, called LR motifs (LRMs), control the precise assembly of DNA repair factors at double-strand break sites. This finding clarifies how the cell selectively recruits proteins for DNA damage response.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • DNA double-strand breaks (DSBs) trigger a complex protein recruitment cascade essential for repair.
  • ATM-dependent phosphorylation and RNF8-mediated ubiquitylation initiate the DSB response.
  • Ubiquitin-binding domains (UBDs) are crucial for assembling DNA repair factors but their ligand selectivity is unclear.

Purpose of the Study:

  • To elucidate the molecular basis for ligand selectivity in the ubiquitin-dependent DNA damage response.
  • To investigate how proteins like RNF168, RNF169, RAD18, and RAP80 are specifically recruited to DSB sites.

Main Methods:

  • Analysis of protein domains and motifs involved in DNA repair factor recruitment.
  • Investigating the function of bipartite modules comprising UBDs and peptide motifs.
  • Assessing the transferability and binding interactions of identified motifs, such as RNF169 LRM2.

Main Results:

  • Identified bipartite modules, consisting of UBDs and specificity-providing LR motifs (LRMs), in RNF168, RNF169, RAD18, and RAP80.
  • Demonstrated that LRMs are transferable and mediate specific protein-ligand interactions.
  • Showed that RNF169 LRM2 binds to nucleosomes, which are substrates for RNF168.

Conclusions:

  • LRM-based ligand selection provides a parsimonious mechanism for building the discrete ubiquitin-signaling pathway in DNA damage response.
  • This mechanism ensures the precise and hierarchical recruitment of DNA repair factors.
  • Understanding LRM function is key to comprehending the fidelity of the DNA damage response.

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