Selective blockage of the 3'→5' exonuclease activity of WRN protein by certain oxidative modifications and bulky lesions in DNA

Amrita Machwe, Ruth Ganunis, Vilhelm A. Bohr, David K. Orren

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

Individuals with mutations in the WRN gene suffer from Werner syndrome, a disease with early onset of many characteristics of normal aging. The WRN protein (WRNp) functions in DNA metabolism, as the purified polypeptide has both 3'→5' helicase and 3'→5' exonuclease activities. In this study, we have further characterized WRNp exonuclease activity by examining its ability to degrade double-stranded DNA substrates containing abnormal and damaged nucleotides. In addition, we directly compared the 3'→5' WRNp exonuclease activity with that of exonuclease III and the Klenow fragment of DNA polymerase I. Our results indicate that the presence of certain abnormal bases (such as uracil and hypoxanthine) does not inhibit the exonuclease activity of WRNp, exonuclease III or Klenow, whereas other DNA modifications, including apurinic sites, 8-oxoguanine, 8-oxoadenine and cholesterol adducts, inhibit or block WRNp. The ability of damaged nucleotides to inhibit exonucleolytic digestion differs significantly between WRNp, exonuclease III and Klenow, indicating that each exonuclease has a distinct mechanism of action. In addition, normal and modified DNA substrates are degraded similarly by full-length WRNp and an N-terminal fragment of WRNp, indicating that the specificity for this activity lies mostly within this region. The biochemical and physiological significance of these results is discussed.

Original languageEnglish
Pages (from-to)2762-2770
Number of pages9
JournalNucleic Acids Research
Volume28
Issue number14
DOIs
StatePublished - Jul 15 2000

ASJC Scopus subject areas

  • Genetics

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