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| The EMBO Journal
(2000) 19, 5259–5266, doi:10.1093/emboj/19.19.5259 |
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Misinsertion and bypass of thymine–thymine dimers by human DNA polymerase  |
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| Agnès Tissier1, Ekaterina G. Frank1, John P. McDonald1, Shigenori Iwai2, Fumio Hanaoka3, 4 and Roger Woodgate1 |
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1 Section on DNA Replication, Repair and Mutagenesis, National Institute of Child Health and Human Development, Bethesda, MD 20892-2725, USA 2 Biomolecular Engineering Research Institute, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan 3 Institute for Molecular and Cellular Biology, Osaka University, and CREST, Japan Science and Technology Corporation, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan 4 The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198, Japan To whom correspondence should be addressed Roger Woodgate, woodgate@helix.nih.gov Received 19 June 2000; Accepted 12 July 2000. |
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| Abstract |
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Human DNA polymerase (pol) is a recently discovered enzyme that exhibits extremely low fidelity on undamaged DNA templates. Here, we show that pol is able to facilitate limited translesion replication of a thymine–thymine cyclobutane pyrimidine dimer (CPD). More importantly, however, the bypass event is highly erroneous. Gel kinetic assays reveal that pol misinserts T or G opposite the 3' T of the CPD  1.5 times more frequently than the correct base, A. While pol is unable to extend the T T mispair significantly, the GT mispair is extended and the lesion completely bypassed, with the same efficiency as that of the correctly paired AT base pair. By comparison, pol readily misinserts two bases opposite a 6-4 thymine–thymine pyrimidine–pyrimidone photoproduct (6-4PP), but complete lesion bypass is only a fraction of that observed with the CPD. Our data indicate, therefore, that pol possesses the ability to insert nucleotides opposite UV photoproducts as well as to perform unassisted translesion replication that is likely to be highly mutagenic. |
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Keywords: DNA polymerase  , DNA polymerase  , Rad30, Rad30B, xeroderma pigmentosum variant |
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