Formation of DNA Lesions, its Prevention and Repair

Abstract

The present review discusses three important aspects which are intimately related to human health at the molecular level. The first aspect is the formation of DNA lesions caused due to the reactions of DNA with certain free radicals known as reactive oxygen species (ROS) and reactive nitrogen oxide species (RNOS). Some of these free radicals are constantly formed in biological systems during the metabolic activities while others can be ascribed to the exposure to radiation or pollution. These species react with DNA bases, particularly guanine, leading to base misparing, mutation and several diseases including cancer. The mechanisms of reactions of certain ROS and RNOS with the DNA bases, particularly guanine or its modifications are discussed. The second aspect discussed here is the role of anti-oxidants some of which are present inside biological systems while others can be taken from external sources as food supplements. Certain endogenous anti-oxidants present in biological systems inhibit the formation of reactive free radicals while others, particularly those taken from outside, scavenge the same through appropriate chemical reactions. The molecular mechanisms of action of several anti-oxidants are discussed. The third aspect discussed here is the working of the complex and intelligent molecular machinery which is constantly active in biological systems and removes or repairs the damaged bases. Molecular mechanisms involved in some of these activities are reviewed. Details of recent theoretical studies on all the three aspects mentioned above are discussed.