Updated in 1/14/2016 4:11:07 AM      Viewed: 70 times      (Journal Article)
Nature structural & molecular biology 13 (5): 414-22 (2006)

WRN exonuclease structure and molecular mechanism imply an editing role in DNA end processing.

J Jefferson P Perry , Steven M Yannone , Lauren G Holden , Chiharu Hitomi , Aroumougame Asaithamby , Seungil Han , Priscilla K Cooper , David J Chen , John A Tainer
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.
DOI: 10.1038/nsmb1088      ISSN: 1545-9993