PMID: 17704764 , Related PDB ids: 2OXM, 2OYT

Authors:

Parker JB, Bianchet MA, Krosky DJ, Friedman JI, Amzel LM, Stivers JT

Title:

Enzymatic capture of an extrahelical thymine in the search for uracil in DNA.

Journal:

Nature. 2007 Sep 27;449(7161):433-7. Epub 2007 Aug 19.

Abstract:

The enzyme uracil DNA glycosylase (UNG) excises unwanted uracil bases in the genome using an extrahelical base recognition mechanism. Efficient removal of uracil is essential for prevention of C-to-T transition mutations arising from cytosine deamination, cytotoxic U*A pairs arising from incorporation of dUTP in DNA, and for increasing immunoglobulin gene diversity during the acquired immune response. A central event in all of these UNG-mediated processes is the singling out of rare U*A or U*G base pairs in a background of approximately 10(9) T*A or C*G base pairs in the human genome. Here we establish for the human and Escherichia coli enzymes that discrimination of thymine and uracil is initiated by thermally induced opening of T*A and U*A base pairs and not by active participation of the enzyme. Thus, base-pair dynamics has a critical role in the genome-wide search for uracil, and may be involved in initial damage recognition by other DNA repair glycosylases.