Direct strand scission in double stranded RNA via a C5-pyrimidine radical.
Direct strand scission in double stranded RNA via a C5-pyrimidine radical.
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DOI：
10.1021/ja300044e
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发表时间：
2012-02-29
影响因子：
15
通讯作者：
Greenberg, Marc M.
中科院分区：
文献类型：
--
作者：
Resendiz, Marino J. E.;Pottiboyina, Venkata;Sevilla, Michael D.;Greenberg, Marc M.
核碱基自由基是核酸暴露于γ-辐射分解时产生的主要活性中间体家族。5,6-二氢嘧啶-5-基自由基(1)，氢原子加成的形式产物和羟基自由基加成的模型，是在单链和双链RNA中由酮前体通过Norrish I型光裂解独立生成的。自由基1在5'邻近的核苷酸上产生直接的链断裂，在自由基产生的初始位置只观察到少量的链断裂。链断裂优先发生在双链RNA中，并且在没有O2的情况下。在厌氧条件下，5,6-二氢嘧啶-5-基自由基(1)的链断裂效率依赖于二级结构，这表明这种反应性可能有助于从羟基自由基反应中提取额外的RNA结构信息。改变5'相邻核苷酸的身份对链断裂的影响很小。在C2'-氢原子被1抽离后，通过β-消除3'-磷酸发生核苷酸间链断裂。随后形成的烯烃阳离子自由基从相互竞争的去质子化途径中产生含有3'-磷酸或3'-脱氧-2'-酮核苷酸末端的RNA片段。酮核苷酸端基在低浓度硫醇存在时更有利，可能是通过将阳离子自由基还原为烯醇。与硫醇的竞争研究表明，5,6-二氢嘧啶-5-基自由基(1)的链断裂速度明显快于5,6-二氢嘧啶-6-基自由基(2)，这与使用G3B3方法预测后者比1稳定2.8 kcal/mol的计算研究一致。
Nucleobase radicals are the major family of reactive intermediates produced when nucleic acids are exposed to γ-radiolysis. 5,6-Dihydrouridin-5-yl radical (1), the formal product of hydrogen atom addition and a model for hydroxyl radical addition was independently generated from a ketone precursor via Norrish Type I photocleavage in single stranded, and double stranded RNA. Radical 1 produces direct strand breaks at the 5'-adjacent nucleotide and only minor amounts of strand scission are observed at the initial site of radical generation. Strand scission occurs preferentially in double stranded RNA and in the absence of O2. The dependence of strand scission efficiency from 5,6-dihydrouridin-5-yl radical (1) on secondary structure under anaerobic conditions suggests that this reactivity may be useful for extracting additional RNA structural information from hydroxyl radical reactions. Varying the identity of the 5'-adjacent nucleotide has little effect on strand scission. Internucleotidyl strand scission occurs via β-elimination of the 3'-phosphate following C2'-hydrogen atom abstraction by 1. The subsequently formed olefin cation radical yields RNA fragments containing 3'-phosphate or 3'-deoxy-2'-ketonucleotide termini from competing deprotonation pathways. The ketonucleotide end group is favored in the presence of low concentrations of thiol, presumably by reducing the cation radical to the enol. Competition studies with thiol show that strand scission from 5,6-dihydrouridin-5-yl radical (1) is significantly faster than from 5,6-dihydrouridin-6-yl radical (2) and is consistent with computational studies using the G3B3 approach that predict the latter to be more stable than 1 by 2.8 kcal/mol.
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影响因子：
15
作者：
Jacobs, Aaron C.;Resendiz, Marino J. E.;Greenberg, Marc M.
通讯作者：
Greenberg, Marc M.
影响因子：
16.6
作者：
Kim, J;Gil, JM;Greenberg, MM
通讯作者：
Greenberg, MM
影响因子：
2.9
作者：
Chen, JY;Stubbe, J
通讯作者：
Stubbe, J
影响因子：
2.1
作者：
HAYAKAWA, H;TANAKA, H;MIYASAKA, T
通讯作者：
MIYASAKA, T
影响因子：
3.6
作者：
Hong, IS;Carter, KN;Greenberg, MM
通讯作者：
Greenberg, MM