Elder Rhoderick H, Dianov Grigory L
Medical Research Council Radiation and Genome Stability Unit, Harwell, Oxfordshire, OX11 0RD, United Kingdom.
J Biol Chem. 2002 Dec 27;277(52):50487-90. doi: 10.1074/jbc.M208153200. Epub 2002 Oct 24.
In mammalian cells, thymine glycols and other oxidized pyrimidines such as 5,6-dihydrouracil are removed from DNA by the NTH1 protein, a bifunctional DNA-N-glycosylase. However, mNTH1 knock-out mice in common with other DNA glycosylase-deficient mice do not show any severe abnormalities associated with accumulation of DNA damage and mutations. In the present study we used an in vitro repair system to investigate the mechanism for the removal of 5,6-dihydrouracil from DNA by mNTH1-deficient cell-free extracts derived from testes of mNTH1 knock-out mice. We found that these extracts are able to support the removal of 5,6-dihydrouracil from DNA at about 20% of the efficiency of normal extracts. Furthermore, we also found that single-nucleotide patch base excision repair is the major pathway for removal of 5,6-dihydrouracil in mNTH1-deficient cell extracts, suggesting the involvement of other DNA glycosylase(s) in the removal of oxidized pyrimidines.
在哺乳动物细胞中，胸腺嘧啶乙二醇和其他氧化嘧啶，如5,6 - 二氢尿嘧啶，可通过NTH1蛋白（一种双功能DNA - N - 糖基化酶）从DNA中去除。然而，与其他DNA糖基化酶缺陷小鼠一样，mNTH1基因敲除小鼠并未表现出与DNA损伤和突变积累相关的任何严重异常。在本研究中，我们使用体外修复系统来研究从mNTH1基因敲除小鼠睾丸中提取的无细胞提取物（缺乏mNTH1）从DNA中去除5,6 - 二氢尿嘧啶的机制。我们发现这些提取物能够以正常提取物约20%的效率支持从DNA中去除5,6 - 二氢尿嘧啶。此外，我们还发现单核苷酸补丁碱基切除修复是mNTH1缺陷细胞提取物中去除5,6 - 二氢尿嘧啶的主要途径，这表明其他DNA糖基化酶参与了氧化嘧啶的去除。
