Efficient removal of formamidopyrimidines by 8-oxoguanine glycosylases

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Oxidative stress generates DNA lesions like formamidopyrimidine (FapyG, FapyA) and 8-oxopurines (OG, OA) from a common intermediate.
• Understanding the repair mechanisms of these lesions is crucial for assessing their mutagenic potential and cellular response.

Purpose of the Study:

• To investigate the excision of FapyG and FapyA lesions by DNA glycosylases Fpg, hOGG1, and Ntg1.
• To determine how base pairing context influences the repair efficiency and selectivity of these enzymes.
• To evaluate the potential role of these repair enzymes in mitigating or exacerbating the mutagenicity of Fapy lesions.

Main Methods:

• Single-turnover kinetic experiments were conducted to measure the excision rates of FapyG and FapyA.
• The influence of various base pair contexts on lesion removal was examined.
• Comparative analysis of lesion removal by Fpg, hOGG1, and Ntg1 was performed.

Main Results:

• All three glycosylases (Fpg, hOGG1, Ntg1) removed FapyG as efficiently as OG, with preference for Watson-Crick pairing (e.g., C).
• Fpg and Ntg1 showed higher activity for FapyA removal than OG, irrespective of the opposing base.
• hOGG1 exhibited less robust removal of FapyA compared to FapyG and OG, with significant activity only when paired with C.

Conclusions:

• The high in vitro activity of glycosylases towards FapyG and FapyA suggests their in vivo relevance in repairing these oxidative DNA lesions.
• Enzyme selectivity based on base pairing context can modulate the mutagenic profiles of Fapy lesions.
• Differential repair efficiencies highlight the complex interplay between DNA damage, repair enzymes, and mutagenesis.