DNA condensation by polyamines: A laser light scattering study of structural effects
DNA condensation by polyamines: A laser light scattering study of structural effects
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DOI：
10.1021/bi010993t
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发表时间：
2001-11-13
期刊：
影响因子：
2.9
通讯作者：
Thomas, TJ
中科院分区：
文献类型：
--
作者：
Vijayanathan, V;Thomas, T;Thomas, TJ
多胺如亚精胺和精胺在活细胞中含量丰富，据信有助于细胞DNA的密集包装。DNA浓缩是基因载体在活细胞中转运的先决条件。为了阐明多胺控制DNA缩合的结构特征，我们用静态和动态光散射技术研究了精胺及其一系列同系物H_2N（CH_2）（3）NH（CH_2）（n=2-12）NH（CH_2）（3）NH_2（对于精胺，n = 4）对λ-DNA的破坏。所有的多胺引起DNA缩合，然而，它们的功效不同的多胺的结构几何形状。在10 mM二甲胂酸钠缓冲液中，对于n = 4-8的精胺同系物，DNA缩合的EC 50值相当（4 μ M），而较低和较高的同系物在较高的EC 50值下引起DNA缩合。EC 50值随着缓冲液中单价离子（Na+）浓度的增加而增加。对数[EC_（50）（多胺（4+））]对对数[Na+]曲线的斜率对于偶数值的多胺类似于1.5，而对于奇数值的化合物类似于1。动态光散射测量显示，对于n = 3-6的化合物，存在流体动力学半径（Rh）为约40-50 nm的致密颗粒。Rh随着分隔多胺仲氨基的亚甲基链长度的进一步增加而增加（对于n = 7-10，Rh = 60-70 nm，对于n = 11和12，Rh> 100 nm）。使用溴化乙锭置换分析测定多胺与DNA的相对结合亲和力表明，与精胺和n = 5和6的同系物相比，n = 2和3的同系物以及n > 7的同系物具有显著较低的DNA结合亲和力。这些数据表明，等价的多胺的化学结构对其识别和凝聚DNA的能力，以及在水溶液中形成的DNA凝聚物的大小产生深远的影响。
Polyamines such as spermidine and spermine are abundant in living cells and are believed to aid in the dense packaging of cellular DNA. DNA condensation is a prerequisite for the transport of gene vectors in living cells. To elucidate the structural features of polyamines governing DNA condensation, we studied the collapse of lambda -DNA by spermine and a series of its homologues, H2N(CH2)(3)NH(CH2)(n=2-12)NH(CH2)(3)NH2 (n = 4 for spermine), using static and dynamic light scattering techniques. All polyamines provoked DNA condensation; however, their efficacy varied with the structural geometry of the polyamine. In 10 mM sodium cacodylate buffer, the EC50 values for DNA condensation were comparable (4 I muM) for spermine homologues with n = 4-8, whereas the lower and higher homologues provoked DNA condensation at higher EC50 values. The EC50 values increased with an increase in the monovalent ion (Na+) concentration in the buffer. The slope of a plot of log [EC50(polyamine(4+))] against log [Na+] was similar to1.5 for polyamines with even number values of n, whereas the slope value was similar to1 for compounds with odd number values of n. Dynamic light scattering measurements showed the presence of compact particles with hydrodynamic radii (Rh) of about 40-50 nm for compounds with n = 3-6. Rh increased with further increase in methylene chain length separating the secondary amino groups of the polyamines (Rh = 60-70 am for n = 7-10 and > 100 nm for n = 11 and 12). Determination of the relative binding affinity of polyamines to DNA using an ethidium bromide displacement assay showed that homologues with n = 2 and 3 as well as those with n > 7 had significantly lower DNA binding affinity compared to spermine and homologues with n = 5 and 6. These data suggest that the chemical structure of isovalent polyamines exerts a profound influence on their ability to recognize and condense DNA, and on the size of the DNA condensates formed in aqueous solution.