Genomic DNA gets damaged by endogenous metabolic byproducts, spontaneous base modifications, and exogenous sources such as UV light, ionizing radiation, and chemical agents. Unrepaired DNA damage is a major source of potentially mutagenic lesions that drive carcinogenesis. DNA repair pathways operate in mammalian cells to maintain genomic integrity. Various proteins are major players in the prevention of genome instability and are directly involved in DNA damage repair.