Selective excision of 5-carboxylcytosine by a thymine DNA glycosylase mutant.

ABSTRACT: The mammalian thymine DNA glycosylase (TDG) excises the mismatched base, uracil, thymine or 5-hydroxymethyluracil (5hmU), as well as removes 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) when paired with a guanine. In the previously solved structure of TDG in complex with DNA containing 5caC, the side chain of asparagine 157 (N157) contacts the 5-carboxyl moiety of 5caC via a weak hydrogen bond. We examined the role of N157 in recognition of 5caC by mutagenesis. The asparagine-to-alanine (N157A) mutant has no detectable base excision activity for a G:T mismatch, and its excision activity is reduced for other substrates including G:5caC. Unexpectedly, the asparagine-to-aspartate (N157D) mutant has a comparable base excision rate for G:5caC substrate to that of wild type, but it only

SUBMITTER: Hashimoto H 

PROVIDER: S-EPMC3594372 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature