PMID:18820296

Citation	Liao, S, Toczylowski, T and Yan, H (2008) Identification of the Xenopus DNA2 protein as a major nuclease for the 5'->3' strand-specific processing of DNA ends. Nucleic Acids Res. 36:6091-100
Abstract	The first step of homology-dependent DNA double-strand break (DSB) repair is the 5' strand-specific processing of DNA ends to generate 3' single-strand tails. Despite extensive effort, the nuclease(s) that is directly responsible for the resection of 5' strands in eukaryotic cells remains elusive. Using nucleoplasmic extracts (NPE) derived from the eggs of Xenopus laevis as the model system, we have found that DNA processing consists of at least two steps: an ATP-dependent unwinding of ends and an ATP-independent 5'-->3' degradation of single-strand tails. The unwinding step is catalyzed by DNA helicases, the major one of which is the Xenopus Werner syndrome protein (xWRN), a member of the RecQ helicase family. In this study, we report the purification and identification of the Xenopus DNA2 (xDNA2) as one of the nucleases responsible for the 5'-->3' degradation of single-strand tails. Immunodepletion of xDNA2 resulted in a significant reduction in end processing and homology-dependent DSB repair. These results provide strong evidence that xDNA2 is a major nuclease for the resection of DNA ends for homology-dependent DSB repair in eukaryotes.
Links	PubMed PMC2577336 Online version:10.1093/nar/gkn616
Keywords	Animals; DNA/chemistry; DNA/metabolism; DNA Breaks, Double-Stranded; DNA Helicases/antagonists & inhibitors; DNA Helicases/isolation & purification; DNA Helicases/metabolism; DNA Repair; DNA, Single-Stranded/metabolism; Endonucleases/antagonists & inhibitors; Endonucleases/isolation & purification; Endonucleases/metabolism; Exodeoxyribonucleases/antagonists & inhibitors; Exodeoxyribonucleases/isolation & purification; Exodeoxyribonucleases/metabolism; Xenopus Proteins/antagonists & inhibitors; Xenopus Proteins/isolation & purification; Xenopus Proteins/metabolism; Xenopus laevis
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
XENLA:DNA2		GO:0008409: 5'-3' exonuclease activity	ECO:0000021:	UniProtKB:Q01588	F		Figure 2B Lanes 3 and 4	complete CACAO 2043
XENLA:DNA2		GO:0045002: double-strand break repair via single-strand annealing	ECO:0000314:		P		Figure 6	complete CACAO 2047
XENLA:DNA2	enables	GO:0008409: 5'-3' exonuclease activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
XENLA:DNA2	involved_in	GO:0045002: double-strand break repair via single-strand annealing	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete

References

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