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Pnk1, a DNA Kinase/Phosphatase Required for Normal Response to DNA Damage by γ-Radiation or Camptothecin inSchizosaccharomyces pombe

2002; Elsevier BV; Volume: 277; Issue: 6 Linguagem: Inglês

10.1074/jbc.m109383200

1083-351X

Maria Meijer, Feridoun Karimi‐Busheri, Timothy Y. Huang, Michael Weinfeld, Dallan Young,

Plant Disease Resistance and Genetics

We report the characterization of Pnk1, a 45-kDa homolog of the human polynucleotide kinase PNKP in Schizosaccharomyces pombe . Recombinant Pnk1 like human PNKP exhibits both 5′-DNA kinase and 3′-DNA phosphatase activities in vitro . Furthermore, we detected 3′-DNA phosphatase activity with a single-stranded substrate in extracts from wild-type yeast, but no activity was detected in pnk1 Δ strains. We have shown that GFP-tagged Pnk1 like mammalian PNKP localizes to the nucleus. Deletion of pnk1 does not affect cell growth under normal conditions but results in significant hypersensitivity to γ-radiation or camptothecin, an inhibitor of topoisomerase I, suggesting that Pnk1 plays an important role in the repair of DNA strand breaks produced by these agents. The pnk1 deletion mutants were not hypersensitive to ethyl methanesulfonate, methyl methanesulfonate, or 4-nitroquinoline N -oxide. Expression of human PNKP in pnk1 Δ cells restores resistance to γ-radiation or camptothecin, suggesting that the functions of yeast Pnk1 and human PNKP have been conserved.