7,8-Dihydro-8-oxoguanine (8-oxoG) is one of the most common oxidative base lesions in normal tissues induced by a variety of endogenous and exogenous agents. Hydantoins are products of 8-oxoG oxidation and as 8-oxoG, they have been shown to be mutagenic lesions. Oxidative DNA damage has been implicated in the etiology of various age-associated pathologies, such as cancer, cardiovascular diseases, arthritis, and several neurodegenerative diseases. The mammalian endonuclease VIII-like 3 (Neil3) is one of the four DNA glycosylases found to recognize and remove hydantoins in the first step of base excision repair (BER) pathway. We have generated mice lacking Neil3 and by using total cell extracts we demonstrate that Neil3 is the main DNA glycosylase that incises hydantoins in single stranded DNA in tissues. Using the neurosphere culture system as a model to study neural stem/progenitor (NSPC) cells we found that lack of Neil3 impaired self renewal but did not affect differentiation capacity. Proliferation was also reduced in mouse embryonic fibroblasts (MEFs) derived from Neil3(-/-) embryos and these cells were sensitive to both the oxidative toxicant paraquat and interstrand cross-link (ICL)-inducing agent cisplatin. Our data support the involvement of Neil3 in removal of replication blocks in proliferating cells.
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