Martynkina L P, Novikova E G, Kolesnikov A A, Strel'tsov S A, Semenov T E, Vengerov Iu Iu
Mol Biol (Mosk). 1989 Nov-Dec;23(6):1645-57.
Studies on compactization and decompactization of the genome are of great importance for elucidation of structural mechanisms taking part in the regulation of gene activity. Kinetoplast DNA (kpDNA) is a convenient model for studies of compactization processes. KpDNA represents unique structure ("network"), consisting of catenated circular molecules of two types: minicircles (900 b.p.) and maxicircles (40 000 b.p.). The compactization process of kpDNA in vitro caused by interaction with synthetic peptide-dansylhydraside trivaline was studied. It was shown that at the initial stages the hairpins are observed on minicircles as if triple rings are being organized. The formation of hairpin is probably favoured by the presence in the minicircles of bent DNA, a specific nucleotide sequence causing rigid bending of the DNA helix. The hairpin does not make contact with the neighbouring DNA segment to form a triple ring, because the sizes of minicircles are too small. The minicircles compactization is finished with a complete collapse of the minicircles with the formation of rod-like structures. The catenation causes branching of rod-like structures. As a result of their intermolecular interaction, the branched rod-like structures become thicker. The process is completed with formation of the compact network, its diameter being 3-6 times smaller compared to the initial one.
对基因组的压缩和去压缩进行研究对于阐明参与基因活性调控的结构机制非常重要。动质体DNA（kpDNA）是研究压缩过程的一个便利模型。kpDNA代表一种独特的结构（“网络”），由两种类型的连环环状分子组成：微小环（900个碱基对）和大环（40000个碱基对）。研究了与合成肽-丹磺酰肼三缬氨酸相互作用导致的kpDNA在体外的压缩过程。结果表明，在初始阶段，微小环上会出现发夹结构，就好像正在形成三环结构。发夹结构的形成可能得益于微小环中存在弯曲的DNA，这种特定的核苷酸序列会导致DNA螺旋发生刚性弯曲。由于微小环的尺寸太小，发夹结构不会与相邻的DNA片段接触形成三环结构。微小环的压缩以微小环完全塌陷并形成棒状结构而告终。连环作用导致棒状结构分支。由于它们的分子间相互作用，分支的棒状结构变得更粗。该过程以形成紧密网络而结束，其直径比初始网络小3至6倍。
