Suppression of spontaneous mutagenesis in human cells by DNA base excision-repair.

The chemical instability of the covalent structure of DNA, and in vivo exposure of DNA to reactive oxygen species and endogenously produced alkylating agents, has triggered the evolution of several specific DNA repair pathways. A major strategy of repair involves the initial removal of an altered base from DNA by a member of the enzyme family of DNA glycosylases. The currently known enzymes of this type in mammalian cells are reviewed, and the subsequent base excision-repair (BER) steps that achieve restoration of the intact DNA structure are also described. The specific problem of retaining high accuracy in this essentially error-free repair process is discussed.