Sequence-specific DNA cleavage by Fe2+-mediated fenton reactions has possible biological implications
Sequence-specific DNA cleavage by Fe2+-mediated fenton reactions has possible biological implications
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DOI：
10.1074/jbc.274.2.962
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发表时间：
1999-01-08
影响因子：
4.8
通讯作者：
Linn, S
中科院分区：
文献类型：
--
作者：
Henle, ES;Han, ZX;Linn, S
已经确定了Fe2+/ h2o2介导的DNA氧化的优先切割位点。在50 mM H2O2条件下，RGGG序列中每个dG片段的核苷5′发生了优先切割，这是大多数端粒重复序列中发现的序列。在含有（TTAGGG）（81）人端粒插入物的质粒中，含有该插入物的限制性片段的链断裂率是相同大小的对照片段的7倍。这一结果表明，端粒DNA可以保护编码DNA免受氧化损伤，并可能将氧化损伤和铁负荷与端粒缩短和衰老联系起来。在微摩尔H2O2条件下，RTGR序列中的胸苷发生了优先裂解，这一序列经常被发现是许多原核生物和真核生物基因对铁或氧胁迫正常反应的启动子所必需的。对B-DNA中Fe2+与RTGR相互作用的计算机模拟表明，由于胸腺嘧啶甲基的位阻作用，Fe2+以一种特定的方式与胸腺嘧啶从碱基堆中翻转出来，从而使Fe2+与三个嘌呤N-7残基形成八面体定向配位。含有ATGA的双寡核苷酸与含有AUGA或A(5m)CGA的双寡核苷酸相比，其核磁共振谱的Fe2+依赖性变化与该模型一致。
Preferential cleavage sites have been determined for Fe2+/H2O2-mediated oxidations of DNA. In 50 mM H2O2, preferential cleavages occurred at the nucleoside 5' to each of the dG moieties in the sequence RGGG, a sequence found in a majority of telomere repeats. Within a plasmid containing a (TTAGGG)(81) human telomere insert, 7-fold more strand breakage occurred in the restriction fragment with the insert than in a similar-sized control fragment. This result implies that telomeric DNA could protect coding DNA from oxidative damage and might also link oxidative damage and iron load to telomere shortening and aging. In micromolar H2O2, preferential cleavage occurred at the thymidine within the sequence RTGR, a sequence frequently found to be required in promoters for normal responses of many procaryotic and eucaryotic genes to iron or oxygen stress. Computer modeling of the interaction of Fe2+ with RTGR in B-DNA suggests that due to steric hindrance with the thymine methyl, Fe2+ associates in a specific manner with the thymine flipped out from the base stack so as to allow an octahedrally-oriented coordination of the Fe2+ with the three purine N-7 residues. Fe2+-dependent changes in NMR spectra of duplex oligonucleotides containing ATGA versus those containing AUGA or A(5m)CGA were consistent with this model.