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Journal of Nucleic Acids
Volume 2010 (2010), Article ID 450926, 9 pages
http://dx.doi.org/10.4061/2010/450926
Review Article

Early Steps in the DNA Base Excision Repair Pathway of a Fission Yeast Schizosaccharomyces pombe

Department of Biochemistry, Faculty of Science, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama 700-0005, Japan

Received 21 June 2010; Accepted 12 August 2010

Academic Editor: Ashis Basu

Copyright © 2010 Kyoichiro Kanamitsu and Shogo Ikeda. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

DNA base excision repair (BER) accounts for maintaining genomic integrity by removing damaged bases that are generated endogenously or induced by genotoxic agents. In this paper, we describe the roles of enzymes functioning in the early steps of BER in fission yeast. Although BER is an evolutionarily conserved process, some unique features of the yeast repair pathway were revealed by genetic and biochemical approaches. AP sites generated by monofunctional DNA glycosylases are incised mainly by AP lyase activity of Nth1p, a sole bifunctional glycosylase in yeast, to leave a blocked end. The major AP endonuclease Apn2p functions predominantly in removing the block. Finally, a DNA polymerase fills the gap, and a DNA ligase seals the nick (Nth1p-dependent or short patch BER). Apn1p backs up Apn2p. In long patch BER, Rad2p endonuclease removes flap DNA containing a lesion after DNA synthesis. A UV-specific endonuclease Uve1p engages in an alternative pathway by nicking DNA on the side of oxidative damage. Nucleotide excision repair and homologous recombination are involved in repair of BER intermediates including the AP site and single-strand break with the block. Other enzymes working in end processing are also discussed.