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首页> 外文期刊>Journal of Molecular Biology >Localization of Fe2+ at an RTGR sequence within a DNA duplex explains preferential cleavage by Fe2+ and H2O2
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Localization of Fe2+ at an RTGR sequence within a DNA duplex explains preferential cleavage by Fe2+ and H2O2

机译：Fe2 +在DNA双链体中RTGR序列处的定位解释了Fe2 +和H2O2的优先切割

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摘要

Nicking of duplex DNA by the iron-mediated Fenton reaction occurs preferentially at a limited number of sequences. Of these, purine-T-G-purine (RTGR) is of particular interest because it is a required element in the upstream regulatory regions of many genes involved in iron and oxidative-stress responses. In order to study the basis of this preferential nicking, NMR studies were undertaken on the RTGR-containing duplex oligonucleotide, d(CGCGATATGACACTAG)/d(CTAGTGTCATATCGCG). One-dimensional and two-dimensional H-1 NMR measurements show that Fe2+ interacts preferentially and reversibly at the ATGA site within the duplex at a rate that is rapid relative to the chemical-shift timescale, while selective paramagnetic NMR line-broadening of the T ATGA guanine H8 suggests that Fe2+ interacts with the guanine N7 moiety. Localization at this site is supported by Fe2+ titrations of a duplex containing a 7-deazaguanine substitution in place of the guanine in the ATGA sequence. The addition of a 100-fold excess of Mg2+ over Fe2+ does not affect the Fe2+-dependent broadening. When the ATGA site in the duplex is replaced by ATGT, an RTGR site (GTGA) is created on the opposite strand. Preferential iron localization then takes place at the 3' guanine in GTGA but no longer at the guanine in ATGT, consistent with the lack of preferential cleavage of ATGT sites relative to ATGA sites.
机译：铁介导的Fenton反应引起的双链DNA切口优先在有限数量的序列上发生。其中，嘌呤-T-G-嘌呤（RTGR）特别令人感兴趣，因为它是参与铁和氧化应激反应的许多基因的上游调节区域中的必需元素。为了研究这种优先刻痕的基础，对含RTGR的双链寡核苷酸d（CGCGATATGACACTAG）/ d（CTAGTGTCATATCGCG）进行了NMR研究。一维和二维H-1 NMR测量结果表明，Fe2 +在双链体的ATGA位点优先且可逆地相互作用，其速率相对于化学位移时间尺度而言是快速的，而T的选择性顺磁NMR线宽化ATGA鸟嘌呤H8提示Fe2 +与鸟嘌呤N7部分相互作用。在该位点的定位由在ATGA序列中含有7-脱氮鸟嘌呤取代的鸟嘌呤替代的双链体的Fe2 +滴定来支持。 Mg2 +比Fe2 +过量100倍并不影响Fe2 +依赖的扩展。当双链体中的ATGA位点被ATGT取代时，在相反链上会创建一个RTGR位点（GTGA）。然后，优先的铁定位发生在GTGA的3'鸟嘌呤处，但不再发生在ATGT的鸟嘌呤中，这与相对于ATGA位点缺乏ATGT位点的优先切割相一致。

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