Formation and Repair of Mismatches Containing Ribonucleotides and Oxidized Bases at Repeated DNA Sequences
Formation and Repair of Mismatches Containing Ribonucleotides and Oxidized Bases at Repeated DNA Sequences
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DOI：
10.1074/jbc.m115.679209
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发表时间：
2015-10-23
影响因子：
4.8
通讯作者：
Mazzei, Filomena
中科院分区：
文献类型：
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作者：
Cilli, Piera;Minoprio, Anna;Mazzei, Filomena
核糖核酸三磷酸(RNTPs)的细胞池比脱氧核糖核酸三磷酸(RNTPs)的细胞池更大。为了确保基因组的稳定性，DNA聚合酶必须区别于rNTPs，并必须通过核苷酸切除修复(RER)去除被掺入的核苷酸。我们研究了DNA聚合酶β(POLβ)将核苷酸整合到三核苷酸重复DNA序列中的能力，以及当提供错误的糖和被氧化的碱基时，碱基切除修复(BER)和RER酶(OGG1、MUTYH和RNase H2)的效率。与7，8-二氢-8-氧鸟嘌呤(8-oxodG)相反的Pol beta将RAMP和RCMP结合在一起，并扩展了这两个错配对。此外，当与da配对时，POL beta能够插入和延长氧化的RGMP。我们发现，当RNaseH2与氧化的碱基配对时，总是保持移除单个核苷酸的能力，或者在DNA双链中切割氧化的核苷酸。相反，BER活性受8-oxodG相反的核苷酸存在的影响。特别是，8-oxodG：RA错配对上的MUTYH活性被完全抑制，尽管其结合能力保持不变。这导致该底物的RNaseH2切割能力降低。因此，由氧化碱基和核苷酸形成的复杂错对可以在重复序列中损害BER和RER。
The cellular pool of ribonucleotide triphosphates (rNTPs) is higher than that of deoxyribonucleotide triphosphates. To ensure genome stability, DNA polymerases must discriminate against rNTPs and incorporated ribonucleotides must be removed by ribo-nucleotide excision repair (RER). We investigated DNA polymerase beta (POL beta) capacity to incorporate ribonucleotides into trinucleotide repeated DNA sequences and the efficiency of base excision repair (BER) and RER enzymes (OGG1, MUTYH, and RNase H2) when presented with an incorrect sugar and an oxidized base. POL beta incorporated rAMP and rCMP opposite 7,8-dihydro-8- oxoguanine (8-oxodG) and extended both mispairs. In addition, POL beta was able to insert and elongate an oxidized rGMP when paired with dA. We show that RNase H2 always preserves the capacity to remove a single ribonucleotide when paired to an oxidized base or to incise an oxidized ribonucleotide in a DNA duplex. In contrast, BER activity is affected by the presence of a ribonucleotide opposite an 8-oxodG. In particular, MUTYH activity on 8-oxodG:rA mispairs is fully inhibited, although its binding capacity is retained. This results in the reduction of RNase H2 incision capability of this substrate. Thus complex mispairs formed by an oxidized base and a ribonucleotide can compromise BER and RER in repeated sequences.