Role of DNA polymerase η in the bypass of a (6-4) TT photoproduct
Role of DNA polymerase η in the bypass of a (6-4) TT photoproduct
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DOI：
10.1128/mcb.21.10.3558-3563.2001
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发表时间：
2001-05-01
影响因子：
5.3
通讯作者：
Prakash, L
中科院分区：
文献类型：
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作者：
Johnson, RE;Haracska, L;Prakash, L
紫外线引起的 DNA 损伤会阻碍正常的复制机制。真核细胞拥有 DNA 聚合酶 eta (Pol eta)，它能够高效、准确地复制顺式胸腺嘧啶胸腺嘧啶 (TT) 二聚体，而人类 Pol eta 的突变会导致易患癌症的综合征，即着色性干皮病的变异形式。在这里，我们测试了 Pol eta 绕过 (6-4) TT 损伤的能力，该损伤比顺式 TT 二聚体更大程度地扭曲 DNA 螺旋。与 (6-4) TT 光产物的 3' T 相对，酵母和人类 Pol eta 都优先插入 G 残基，但它们无法从插入的核苷酸延伸。 DNA Pol eta 对于 UV 诱导诱变至关重要，可有效地从 Pol eta 插入的 (6-4) TT 损伤的 3' T 对面的 G 残基开始延伸，而 Pol zeta 则在损伤的 5' T 对面插入正确的核苷酸 A。因此，(6-4)TT光产物的有效旁路是通过Pol eta和Pol zeta的联合作用实现的，其中Pol eta插入与病变3'T相对的核苷酸，Pol zeta从其延伸。这些生化观察结果与酵母遗传研究相一致，表明突变主要发生在 (6-4) TT 光产物的 3' T 处，并且这些突变经常表现出 3' T -->C 变化，这是由于在 (6-4) TT 损伤的 3' T 对面插入 G 所致。
UV light-induced DNA lesions block the normal replication machinery. Eukaryotic cells possess DNA polymerase eta (Pol eta), which has the ability to replicate past a cis-syn thymine thymine (TT) dimer efficiently and accurately, and mutations in human Pol eta result in the cancer-prone syndrome, the variant form of xeroderma pigmentosum. Here, we test Pol eta for its ability to bypass a (6-4) TT lesion which distorts the DNA helix to a much greater extent than a cis-syn TT dimer, Opposite the 3' T of a (6-4) TT photoproduct, both yeast and human Pol eta preferentially insert a G residue, but they are unable to extend from the inserted nucleotide. DNA Pol eta, essential for UV induced mutagenesis, efficiently extends from the G residue inserted opposite the 3' T of the (6-4) TT lesion by Pol eta, and Pol zeta inserts the correct nucleotide A opposite the 5' T of the lesion. Thus, the efficient bypass of the (6-4) TT photoproduct is achieved by the combined action of Pol eta and Pol zeta, wherein Pol eta inserts a nucleotide opposite the 3' T of the lesion and Pol zeta extends from it. These biochemical observations are in concert with genetic studies in yeast indicating that mutations occur predominantly at the 3' T of the (6-4) TT photoproduct and that these mutations frequently exhibit a 3' T -->C change that would result from the insertion of a G opposite the 3' T of the (6-4) TT lesion.