Nature Structural & Molecular Biology
- 13, 414 - 422 (2006)
Published online: 23 April 2006; | doi:10.1038/nsmb1088
WRN exonuclease structure and molecular mechanism imply an editing role in DNA end processingJ Jefferson P Perry1, 2, Steven M Yannone2, Lauren G Holden1, Chiharu Hitomi1, Aroumougame Asaithamby4, Seungil Han2, 3, Priscilla K Cooper2, David J Chen4 & John A Tainer1, 21
Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA. 2
Life Sciences Division, Department of Molecular Biology, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. 3
Pfizer Global Research and Development, Exploratory Medicinal Sciences (EMS), MS4039 Eastern Point Road, Groton, Connecticut 06340, USA. 4
Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9187, USA.
Correspondence should be addressed to John A Tainer jat@scripps.edu or Steven M Yannone smyannone@lbl.gov WRN is unique among the five human RecQ DNA helicases in having a functional exonuclease domain (WRN-exo) and being defective in the premature aging and cancer-related disorder Werner syndrome. Here, we characterize WRN-exo crystal structures, biochemical activity and participation in DNA end joining. Metal-ion complex structures, active site mutations and activity assays reveal a nuclease mechanism mediated by two metal ions. The DNA end–binding Ku70/80 complex specifically stimulates WRN-exo activity, and structure-based mutational inactivation of WRN-exo alters DNA end joining in human cells. We furthermore establish structural and biochemical similarities of WRN-exo to DnaQ-family replicative proofreading exonucleases, describing WRN-specific adaptations consistent with double-stranded DNA specificity and functionally important conformational changes. These results indicate WRN-exo is a human DnaQ family member and support DnaQ-like proofreading activities stimulated by Ku70/80, with implications for WRN functions in age-related pathologies and maintenance of genomic integrity.
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