[Recent studies on mammalian DNA repair mechanisms].

Errors in the replication of DNA are a major source of spontaneous mutation and a number of cellular functions correct these errors to maintain a low frequency of spontaneous mutation. First, we focused on two enzymes, 8-oxo-dGTPase and O6-methylguanine-DNA methyltransferase, which may be involved in the processes of spontaneous and induced mutagenesis, respectively. These enzymes are present in various organisms, from bacteria to mammalian cells, and appears to be responsible for preventing the occurrence of such mutations at the pre-replicational step. In addition to these two, the other mechanisms, such as nucleotide excision repair and mismatch repair, that also keep mutation rate low we reviewed. Genetic defects in one of the genes involved in DNA repair mechanisms have been linked to the high incidence of cancer, such as Xeroderma pigmentosum and hereditary nonpolyposis colorectal cancer.