A read-ahead function in archaeal DNA polymerases detects promutagenic template-strand uracil
- Martin A. Greagg*,†,
- Mark J. Fogg†,‡,
- George Panayotou§,¶,
- Steven J. Evans‡,
- Bernard A. Connolly‡, and
- Laurence H. Pearl*,‖
- *Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom; §Ludwig Institute for Cancer Research, University College London, 91 Riding House Street, London W1P 8BT, United Kingdom; ‡Department of Biochemistry and Genetics, University of Newcastle, Newcastle upon Tyne, NE2 4HH, United Kingdom; and ¶Institute of Molecular Oncology, Biomedical Sciences Research Centre “A. Fleming,” 14–16 Fleming Street, Vari 166 72, Greece
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Edited by Stephen J. Benkovic, Pennsylvania State University, University Park, PA, and approved April 27, 1999 (received for review February 10, 1999)
Abstract
Deamination of cytosine to uracil is the most common promutagenic change in DNA, and it is greatly increased at the elevated growth temperatures of hyperthermophilic archaea. If not repaired to cytosine prior to replication, uracil in a template strand directs incorporation of adenine, generating a G⋅C → A⋅U transition mutation in half the progeny. Surprisingly, genomic analysis of archaea has so far failed to reveal any homologues of either of the known families of uracil-DNA glycosylases responsible for initiating the base-excision repair of uracil in DNA, which is otherwise universal. Here we show that DNA polymerases from several hyperthermophilic archaea (including Vent and Pfu) specifically recognize the presence of uracil in a template strand and stall DNA synthesis before mutagenic misincorporation of adenine. A specific template-checking function in a DNA polymerase has not been observed previously, and it may represent the first step in a pathway for the repair of cytosine deamination in archaea.
Footnotes
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↵ † M.A.G. and M.J.F. contributed equally to this work.
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↵ ‖ To whom reprint requests should be addressed. E-mail: l.pearl{at}biochem.ucl.ac.uk.
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This paper was submitted directly (Track II) to the Proceedings Office.
- ABBREVIATION:
- exo,
- exonuclease activity
- Copyright © 1999, The National Academy of Sciences
