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Structure of a NHEJ polymerase-mediated DNA synaptic complex
Nigel C Brissett1, Robert S Pitcher, Raquel Juarez
1Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK.
Science (New York, N.Y.)
|October 20, 2007
Summary
Nonhomologous end joining (NHEJ) repairs DNA double-strand breaks using Ku and ligase D (LigD). The LigD polymerase domain structures DNA ends, revealing interactions crucial for genome stability.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Nonhomologous end joining (NHEJ) is a vital DNA double-strand break (DSB) repair pathway.
- Prokaryotes utilize a minimal NHEJ system comprising Ku and ligase D (LigD) for DSB repair during stationary phase.
Purpose of the Study:
- To elucidate the structural and mechanistic basis of DNA end synapsis mediated by the LigD polymerase domain in NHEJ.
- To understand the role of protein-DNA interactions in the NHEJ pathway.
Main Methods:
- X-ray crystallography to determine the structure of Mycobacterium tuberculosis LigD polymerase domain bound to DNA.
- Biochemical and biophysical assays to study DNA end synapsis in solution.
Main Results:
- The crystal structure revealed diverse interactions between LigD and noncomplementary DNA ends, including microhomology pairing, base mismatches, and hairpin-like termini.
- Polymerase-induced DNA end synapsis was confirmed to occur in solution.
Conclusions:
- The observed DNA synaptic structure represents a key intermediate in the NHEJ pathway.
- Both the LigD polymerase and DNA sequence dictate the order of synapsis and remodeling events preceding DNA ligation.
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