Werner protein protects nonproliferating cells from oxidative DNA damage.
Werner syndrome, caused by mutations of the WRN gene, mimics many changes of normal aging. Although roles for WRN protein in DNA replication, recombination, and telomere maintenance have been suggested, the pathology of rapidly dividing cells is not a feature of Werner syndrome. To identify cellular events that are specifically vulnerable to WRN deficiency, we used RNA interference (RNAi) to knockdown WRN or BLM (the RecQ helicase mutated in Bloom syndrome) expression in primary human fibroblasts. Withdrawal of WRN or BLM produced accelerated cellular senescence phenotype and DNA damage response in normal fibroblasts, as evidenced by induction of gammaH2AX and 53BP1 nuclear foci. After WRN depletion, the induction of these foci was seen most prominently in nondividing cells. Growth in physiological (3%) oxygen or in the presence of an antioxidant prevented the development of the DNA damage foci in WRN-depleted cells, whereas acute oxidative stress led to inefficient repair of the lesions. Furthermore, WRN RNAi-induced DNA damage was suppressed by overexpression of the telomere-binding protein TRF2. These conditions, however, did not prevent the DNA damage response in BLM-ablated cells, suggesting a distinct role for WRN in DNA homeostasis in vivo. Thus, manifestations of Werner syndrome may reflect an impaired ability of slowly dividing cells to limit oxidative DNA damage.
Szekely
Anna M
AM
Department of Genetics, Yale University School of Medicine, TAC Bldg., Rm. S319, 300 Cedar St., New Haven, CT 06510, USA.
Bleichert
Franziska
F
Nümann
Astrid
A
Van Komen
Stephen
S
Manasanch
Elisabeth
E
Ben Nasr
Abdelhakim
A
Canaan
Allon
A
Weissman
Sherman M
SM
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence; D004247:DNA / Q000235:genetics*; D004249:DNA Damage / Q000187:drug effects; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D005090:Exodeoxyribonucleases; D005347:Fibroblasts; D005786:Gene Expression Regulation; D006801:Humans; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000502:physiology*; D010100:Oxygen / Q000494:pharmacology; D034622:RNA Interference; D053484:RecQ Helicases; D035341:Telomeric Repeat Binding Protein 2 / Q000235:genetics / Q000378:metabolism; D000071657:Werner Syndrome Helicase
D035341:Telomeric Repeat Binding Protein 2; D004247:DNA; D005090:Exodeoxyribonucleases; D000251:Adenosine Triphosphatases; C097151:Bloom syndrome protein; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase; D010100:Oxygen