Arwood L J, Spiker S
Department of Genetics, North Carolina State University, Raleigh 27695-7614.
J Biol Chem. 1990 Jun 15;265(17):9771-7.
We have used an electrophoretic retardation assay to investigate the interactions of wheat high mobility group (HMG) proteins with DNA and with isolated trimmed mononucleosomes (complexes which contain a histone octamer and approximately 146 base pairs of DNA). In order to characterize these interactions, we have compared the binding of each of the wheat HMG proteins, HMGa, b, c, and d, with those of the low molecular weight chicken HMG proteins HMG14 and 17. These vertebrate animal HMG proteins have previously been shown to occupy two specific binding sites on animal nucleosomes and to have a greater affinity for nucleosomes than for naked DNA (Mardian, J. K. W., Paton, A. E., Bunick, G. J., and Olins, D. E. (1980) Science 209, 1534-1536; Sandeen, G., Wood, W. I., and Felsenfeld, G. (1980) Nucleic Acids Res. 8, 3757-3778). As a criterion for "specific binding," we have used the property of HMG14 and 17 binding of causing a discontinuous shift of nucleosomes to a distinct band of lower electrophoretic mobility. According to this criterion, wheat HMGb, c, and d do not bind nucleosomes specifically. These HMG proteins have approximately the same affinity for nucleosomes and naked DNA. Wheat HMGa does bind nucleosomes specifically by this criterion, but other aspects of the binding are reminiscent of histone H1-nucleosome binding. We present evidence that trimmed mononucleosomes of wheat are conformationally distinct from their animal counterparts. Despite the conformational differences, competition studies indicate that chicken and wheat mononucleosomes have essentially identical affinity for the low molecular weight animal HMG proteins.
我们使用了电泳阻滞分析法来研究小麦高迁移率族（HMG）蛋白与DNA以及与分离的修剪单核小体（包含组蛋白八聚体和约146个碱基对DNA的复合物）之间的相互作用。为了表征这些相互作用，我们将小麦的每种HMG蛋白HMGa、b、c和d与低分子量鸡HMG蛋白HMG14和17的结合情况进行了比较。这些脊椎动物的HMG蛋白先前已被证明可占据动物核小体上的两个特定结合位点，并且对核小体的亲和力比对裸露DNA的亲和力更高（Mardian, J. K. W., Paton, A. E., Bunick, G. J., and Olins, D. E. (1980) Science 209, 1534 - 1536; Sandeen, G., Wood, W. I., and Felsenfeld, G. (1980) Nucleic Acids Res. 8, 3757 - 3778）。作为“特异性结合”的标准，我们利用了HMG14和17结合导致核小体向较低电泳迁移率的独特条带发生不连续迁移的特性。根据这一标准，小麦HMGb、c和d不特异性结合核小体。这些HMG蛋白对核小体和裸露DNA的亲和力大致相同。按照这一标准，小麦HMGa确实特异性结合核小体，但结合的其他方面让人联想到组蛋白H1与核小体的结合。我们提供的证据表明，小麦的修剪单核小体在构象上与其动物对应物不同。尽管存在构象差异，但竞争研究表明，鸡和小麦的单核小体对低分子量动物HMG蛋白的亲和力基本相同。
