Nucleic Acids Research Advance Access originally published online on August 21, 2007
Nucleic Acids Research 2007 35(17):5672-5682; doi:10.1093/nar/gkm592
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Nucleic Acids Research, 2007, Vol. 35, No. 17 5672-5682
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Psoralen-induced DNA adducts are substrates for the base excision repair pathway in human cells
1Group «DNA repair», UMR 8126 of CNRS and 2Group «FANC/BRCA pathway and Cancer» FRE2939 of CNRS, University of Paris-South, Institute Gustave Roussy, Villejuif Cedex, F-94805, France
*To whom correspondence should be addressed. Tel: +33 1 42115404; Fax: +33 1 42115276; Email: smurat{at}igr.fr
Correspondence may also be addressed to Filippo Rosselli. Tel: +33 1 42115116; Fax: +33 1 42115008; Email: rosselli{at}igr.fr
Received May 3, 2007. Revised July 18, 2007. Accepted July 18, 2007.
Interstrand cross-link (ICL) is a covalent modification of both strands of DNA, which prevents DNA strand separation during transcription and replication. Upon photoactivation 8-methoxypsoralen (8-MOP+UVA) alkylates both strands of DNA duplex at the 5,6-double bond of thymidines, generating monoadducts (MAs) and ICLs. It was thought that bulky DNA lesions such as MAs are eliminated only in the nucleotide excision repair pathway. Instead, non-bulky DNA lesions are substrates for DNA glycosylases and AP endonucleases which initiate the base excision repair (BER) pathway. Here we examined whether BER might be involved in the removal of psoralen–DNA photoadducts. The results show that in human cells DNA glycosylase NEIL1 excises the MAs in duplex DNA, subsequently the apurinic/apyrimidinic endonuclease 1, APE1, removes the 3'-phosphate residue at single-strand break generated by NEIL1. The apparent kinetic parameters suggest that NEIL1 excises MAs with high efficiency. Consistent with these results HeLa cells lacking APE1 and/or NEIL1 become hypersensitive to 8-MOP+UVA exposure. Furthermore, we demonstrate that bacterial homologues of NEIL1, the Fpg and Nei proteins, also excise MAs. New substrate specificity of the Fpg/Nei protein family provides an alternative repair pathway for ICLs and bulky DNA damage.
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