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Sequence context- and temperature-dependent nucleotide excision repair of a benzo[a]pyrene diol epoxide-guanine DNA adduct catalyzed by thermophilic UvrABC proteins.

Abstract：

:The influence of DNA base sequence context on the removal of a bulky benzo[a]pyrene diol epoxide-guanine adduct, (+)-trans-B[a]P-N2-dG (G*), by UvrABC nuclease from the thermophilic organism Bacillus caldotenax was investigated. The lesion was flanked by either T or C in otherwise identical complementary 43-mer duplexes (TG*T or CG*C, respectively). It was reported earlier that in the CG*C context, a dominant minor groove adduct structure was observed by NMR methods with all Watson-Crick base pairs intact, and the duplex exhibited a rigid bend. In contrast, in the TG*T context, a highly flexible bend was observed, base pairing at G*, and two 5'-base pairs flanking the adduct were impaired, and multiple solvent-accessible adduct conformations were observed. The TG*T-43-mer duplexes are incised with consistently greater efficiency by UvrABC proteins from B. caldotenax by a factor of 2.3 +/- 0.3. The rates of incisions increase with increasing temperature and are characterized by linear Arrhenius plots with activation energies of 27.0 +/- 1.5 and 23.4 +/- 1.0 kcal/mol for CG*C and TG*T duplexes, respectively. These values reflect the thermophilic characteristics of the UVrABC nuclease complex and the contributions of the different DNA substrates to the overall activation energies. These effects are consistent with base sequence context-dependent differences in structural disorder engendered by a loss of local base stacking interactions and Watson-Crick base pairing in the immediate vicinity of the lesions in the TG*T duplexes. The local weakening of base pairing interactions constitutes a recognition element of the UvrABC nucleotide excision repair apparatus.

journal_name

Biochemistry

journal_title

Biochemistry

authors

Ruan Q,Liu T,Kolbanovskiy A,Liu Y,Ren J,Skorvaga M,Zou Y,Lader J,Malkani B,Amin S,Van Houten B,Geacintov NE

doi

10.1021/bi700294k

subject

Has Abstract

pub_date

2007-06-12 00:00:00

pages

7006-15

issue

eissn

0006-2960

issn

1520-4995

journal_volume

pub_type

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Sequence context- and temperature-dependent nucleotide excision repair of a benzo[a]pyrene diol epoxide-guanine DNA adduct catalyzed by thermophilic UvrABC proteins.