碱基切除修复
碱基切除修复（Base excision repair，BER）是细胞修复受损DNA的一种机制，主要用来修补大小较小、对DNA双股螺旋结构影响较小的损伤，包括去胺、被烷基化或氧化的碱基，如8-羟基鸟嘌呤（8-oxoG）、7-甲基鸟苷、黄嘌呤与尿嘧啶等[1][2]。大小较大、影响DNA结构较大的损伤（如紫外线造成的胸腺嘧啶二聚体）则是由核苷酸切除修复（NER）途径修补[3]。细菌[4]、古菌[5]与真核生物皆有碱基切除修复的机制。
BER的过程首先由DNA糖基酶移除损伤的碱基，形成AP位点，随后AP核酸内切酶将此位点的磷酸二酯键切除，造成DNA单股断裂，接著再由DNA聚合酶合成缺失的碱基（与一般DNA复制的过程一样有DNA夹参与），可能仅合成单一缺失的碱基后由DNA连接酶完成修补（短补丁修复；short-patch BER），也可能合成2-10个核苷酸以取代下游的若干的核苷酸，由Flap核酸内切酶将旧有的核苷酸切除后，再由DNA连接酶完成修补（长补丁修复；long-patch BER）[6]，两途径的选择由DNA损伤种类、细胞周期、细胞分化状态与物种种类等因素决定[7]。
DNA糖基酶的活性可能随老化而下降，使BER途径的效率降低[8]。另外BER途径的缺失与数种癌症有关[9][10]。
参考文献
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- ^ Jayanta Chaudhuri; Frederick W. Alt. Class-switch recombination: interplay of transcription, DNA deamination and DNA repair. Nature Reviews Immunology. 2004, 4 (7): 541–552. PMID 15229473. doi:10.1038/nri1395.
- ^ Reardon JT, Sancar A. Purification and characterization of Escherichia coli and human nucleotide excision repair enzyme systems. Methods in Enzymology. 2006, 408: 189–213. ISBN 9780121828134. PMID 16793370. doi:10.1016/S0076-6879(06)08012-8.
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- ^ Liu Y, Prasad R, Beard WA, Kedar PS, Hou EW, Shock DD, Wilson SH. Coordination of Steps in Single-nucleotide Base Excision Repair Mediated by Apurinic/Apyrimidinic Endonuclease 1 and DNA Polymerase β. Journal of Biological Chemistry. 2007, 282 (18): 13532–13541. PMC 2366199 . PMID 17355977. doi:10.1074/jbc.M611295200.
- ^ Fortini P, Dogliotti E. Base damage and single-strand break repair: mechanisms and functional significance of short- and long-patch repair subpathways. DNA Repair. April 2007, 6 (4): 398–409. PMID 17129767. doi:10.1016/j.dnarep.2006.10.008.
- ^ Atamna H, Cheung I, Ames BN. A method for detecting abasic sites in living cells: age-dependent changes in base excision repair. Proc. Natl. Acad. Sci. U.S.A. 2000, 97 (2): 686–91. PMC 15391 . PMID 10639140. doi:10.1073/pnas.97.2.686.
- ^ Chaisaingmongkol J, Popanda O, Warta R, Dyckhoff G, Herpel E, Geiselhart L, Claus R, Lasitschka F, Campos B, Oakes CC, Bermejo JL, Herold-Mende C, Plass C, Schmezer P. Epigenetic screen of human DNA repair genes identifies aberrant promoter methylation of NEIL1 in head and neck squamous cell carcinoma. Oncogene. 2012, 31 (49): 5108–16. PMID 22286769. doi:10.1038/onc.2011.660.
- ^ Farrington, S. M.; Tenesa, A; Barnetson, R; Wiltshire, A; Prendergast, J; Porteous, M; Campbell, H; Dunlop, M. G. Germline susceptibility to colorectal cancer due to base-excision repair gene defects. The American Journal of Human Genetics. 2005, 77 (1): 112–9. PMC 1226182 . PMID 15931596. doi:10.1086/431213.
