A structural rationale for stalling of a replicative DNA polymerase at the most common oxidative thymine lesion, thymine glycol.

Abstract

Thymine glycol (Tg) is a common product of oxidation and ionizing radiation, including that used for cancer treatment. Although Tg is a poor mutagenic lesion, it has been shown to present a strong block to both repair and replicative DNA polymerases. The 2.65-A crystal structure of a binary complex of the replicative RB69 DNA polymerase with DNA shows that the templating Tg is intrahelical and forms a regular Watson-Crick base pair with the incorporated A. The C5 methyl group protrudes axially from the ring of the damaged pyrimidine and hinders stacking of the adjacent 5' template guanine. The position of the displaced 5' template guanine is such that the next incoming nucleotide cannot be incorporated into the growing primer strand, and it explains why primer extension past the lesion is prohibited even though DNA polymerases can readily incorporate an A across from the Tg lesion.

• Authors: Pierre Aller, Mark A Rould, Matthew Hogg, Susan S Wallace, Sylvie Doublié
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 104 Issue 3 Pg. 814-8 (Jan 16 2007) ISSN: 0027-8424 [Print] United States
• PMID: 17210917 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• DNA
• DNA-Directed DNA Polymerase
• Thymine

Topics

• Crystallography, X-Ray
• DNA (chemistry, metabolism)
• DNA Replication
• DNA-Directed DNA Polymerase (chemistry, genetics, metabolism)
• Models, Molecular
• Nucleic Acid Conformation
• Oxidation-Reduction
• Protein Structure, Tertiary
• Thymine (analogs & derivatives, chemistry, metabolism)