Sequence Context- and Temperature-Dependent Nucleotide Excision Repair of a Benzo[a]pyrene Diol Epoxide-Guanine DNA Adduct Catalyzed by Thermophilic UvrABC Proteins

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• 作者：Qian Ruan ; Tongming Liu ; Alexander Kolbanovskiy ; Yang Liu ; Jian Ren ; Milan Skorvaga ; Yue Zou ; Joshua Lader ; Brijesh Malkani ; Shantu Amin ; Bennett Van Houten ; Nicholas E. Geacintov
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：June 12, 2007
• 年：2007
• 卷：46
• 期：23
• 页码：7006 - 7015
• 全文大小：455K
• 年卷期：v.46,no.23(June 12, 2007)
• ISSN：1520-4995

文摘

The influence of DNA base sequence context on the removal of a bulky benzo[a]pyrene diolepoxide-guanine adduct, (+)-trans-B[a]P-N²-dG (G*), by UvrABC nuclease from the thermophilic organismBacillus caldotenax was investigated. The lesion was flanked by either T or C in otherwise identicalcomplementary 43-mer duplexes (TG*T or CG*C, respectively). It was reported earlier that in the CG*Ccontext, 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 highlyflexible 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 areincised 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 Arrheniusplots 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 andthe contributions of the different DNA substrates to the overall activation energies. These effects areconsistent with base sequence context-dependent differences in structural disorder engendered by a lossof local base stacking interactions and Watson-Crick base pairing in the immediate vicinity of the lesionsin the TG*T duplexes. The local weakening of base pairing interactions constitutes a recognition elementof the UvrABC nucleotide excision repair apparatus.