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1: J Biol Chem. 2006 Aug 18;281(33):23445-55. Epub 2006 Jun 19.
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Erratum in:
  • J Biol Chem. 2007 Apr 27;282(17):13139.

Human DNA polymerase N (POLN) is a low fidelity enzyme capable of error-free bypass of 5S-thymine glycol.

Takata K, Shimizu T, Iwai S, Wood RD.

Department of Pharmacology, Hillman Cancer Center, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15213-1863, USA.

Human DNA polymerase N (POLN or pol nu) is the most recently discovered nuclear DNA polymerase in the human genome. It is an A-family DNA polymerase related to Escherichia coli pol I, human POLQ, and Drosophila Mus308. We report the first purification of the recombinant enzyme and examination of its biochemical properties, as a step toward understanding the functions of POLN. Unusual for an A-family DNA polymerase, POLN is a low fidelity enzyme incorporating T opposite template G with a frequency of 0.45 and G opposite template T with a frequency of 0.021. The frequency of misincorporation of T opposite template G is higher than any other known DNA polymerase. POLN has a processivity of DNA synthesis (1-100 nucleotides) similar to the exonuclease-deficient Klenow fragment of E. coli pol I, is inhibited by dideoxynucleotides, and resistant to aphidicolin. The strand displacement activity of POLN was higher than exonuclease-deficient Klenow fragment. Furthermore, POLN can perform translesion synthesis past thymine glycol, a common endogenous and radiation-induced product of reactive oxygen species damage to DNA. Thymine glycol blocks DNA synthesis by most DNA polymerases, but POLN was particularly adept at efficient and accurate translesion synthesis past a 5S-thymine glycol.

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PMID: 16787914 [PubMed - indexed for MEDLINE]