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Molecular and Cellular Biology, November 2001, p. 7191-7198, Vol. 21, No. 21
Department of Pathology, University of
Michigan Medical School, Ann Arbor, Michigan 48109-0602
Received 11 May 2001/Returned for modification 12 June
2001/Accepted 1 August 2001
In Saccharomyces cerevisiae, the
apurinic/apyrimidinic (AP) endonucleases Apn1 and Apn2 act as
alternative pathways for the removal of various 3'-terminal blocking
lesions from DNA strand breaks and in the repair of abasic sites, which
both result from oxidative DNA damage. Here we demonstrate that Tpp1, a
homologue of the 3' phosphatase domain of polynucleotide kinase, is a
third member of this group of redundant 3' processing enzymes. Unlike Apn1 and Apn2, Tpp1 is specific for the removal of 3' phosphates at
strand breaks and does not possess more general 3' phosphodiesterase, exonuclease, or AP endonuclease activities. Deletion of
TPP1 in an apn1 apn2 mutant background
dramatically increased the sensitivity of the double mutant to DNA
damage caused by H2O2 and bleomycin but not to
damage caused by methyl methanesulfonate. The triple mutant was
also deficient in the repair of 3' phosphate lesions left by
Tdp1-mediated cleavage of camptothecin-stabilized Top1-DNA covalent
complexes. Finally, the tpp1 apn1 apn2 triple mutation displayed synthetic lethality in combination with rad52,
possibly implicating postreplication repair in the removal of
unrepaired 3'-terminal lesions resulting from endogenous damage. Taken
together, these results demonstrate a clear role for the
lesion-specific enzyme, Tpp1, in the repair of a subset of DNA strand breaks.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.21.7191-7198.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Repair of DNA Strand Breaks by the Overlapping
Functions of Lesion-Specific and Non-Lesion-Specific DNA
3' Phosphatases
*
Corresponding author. Mailing address: Department of
Pathology, University of Michigan Medical School, 1301 Catherine Rd., M4214 Med. Sci. I, Box 0602, Ann Arbor, MI 48109-0602. Phone: (734)
936-1887. Fax: (734) 763-6476. E-mail: wilsonte{at}umich.edu.
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