The versatile thymine DNA-glycosylase:: a comparative characterization of the human, Drosophila and fission yeast orthologs
The versatile thymine DNA-glycosylase:: a comparative characterization of the human, Drosophila and fission yeast orthologs
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DOI：
10.1093/nar/gkg344
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发表时间：
2003-05-01
影响因子：
14.9
通讯作者：
Schär, P
中科院分区：
文献类型：
--
作者：
Hardeland, U;Bentele, M;Schär, P
人胸腺嘧啶-DNA糖基化酶（TDG）是一种能将G.T和G.U错配的胸腺嘧啶和尿嘧啶分别切除的酶，它通过自发脱氨基5-甲基胞嘧啶和胞嘧啶，在细胞防御基因突变中发挥重要作用。在这项研究中，我们的特点是两个新发现的直向同源的TDG，黑腹果蝇Thd 1 p和裂殖酵母Thp 1 p蛋白，目的是解决这个亚家族的尿嘧啶-DNA糖基化酶从进化的角度来看的功能。一个系统的生化比较，这两种酶与人类TDG揭示了一些具有生物学意义的事实。(i)所有真核TDG直向同源物都具有广泛的和物种特异性的底物谱，包括各种受损的嘧啶和嘌呤碱基;（ii）在任何双链DNA背景下，所有底物中最常见的最有效加工的底物是尿嘧啶和3，N4-乙烯胞嘧啶，与鸟嘌呤和5-氟尿嘧啶相反;（iii）5-甲基胞嘧啶和胸腺嘧啶衍生物仅由人和果蝇酶以可观的效率加工;（iv）没有一种蛋白质能够水解与G相对的未损伤的5 ′-甲基胞嘧啶;和（v）酶的双链和错配依赖性随底物而变化，并且不是DNA糖基化酶的该亚家族的严格特征。这些发现推进了我们目前对TDG蛋白的作用的看法，并证明它们已经进化出了高结构灵活性，以根据个体物种的特定需求对抗广泛的DNA碱基损伤。
Human thymine-DNA glycosylase (TDG) is well known to excise thymine and uracil from G.T and G.U mismatches, respectively, and was therefore proposed to play a central role in the cellular defense against genetic mutation through spontaneous deamination of 5-methylcytosine and cytosine. In this study, we characterized two newly discovered orthologs of TDG, the Drosophila melanogaster Thd1p and the Schizosaccharomyces pombe Thp1p proteins, with an objective to address the function of this subfamily of uracil-DNA glycosylases from an evolutionary perspective. A systematic biochemical comparison of both enzymes with human TDG revealed a number of biologically significant facts. (i) All eukaryotic TDG orthologs have broad and species-specific substrate spectra that include a variety of damaged pyrimidine and purine bases; (ii) the common most efficiently processed substrates of all are uracil and 3,N4- ethenocytosine opposite guanine and 5-fluorouracil in any double-stranded DNA context; (iii) 5-methylcytosine and thymine derivatives are processed with an appreciable efficiency only by the human and the Drosophila enzymes; (iv) none of the proteins is able to hydrolyze a non-damaged 5'-methylcytosine opposite G; and (v) the double strand and mismatch dependency of the enzymes varies with the substrate and is not a stringent feature of this subfamily of DNA glycosylases. These findings advance our current view on the role of TDG proteins and document that they have evolved with high structural flexibility to counter a broad range of DNA base damage in accordance with the specific needs of individual species.