EFFECTS OF DNA SUPERCOILING ON THE TOPOLOGICAL PROPERTIES OF NUCLEOSOMES

DNA 超螺旋对核小体拓扑性质的影响

• 批准号: 3917767
• 负责人: M GELLERT
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3917767
• 关键词: DNA gyrase; circular DNA; conformation; genetic manipulation; histones; nucleobase; nucleosomes; plasmids; protein reconstitution

In the nucleosome core particle, at least 145 base pairs of DNA are bound to the histone octamer in a superhelical conformation. We have asked what effect the presence of these particles has on the ability of DNA gyrase to supercoil DNA. Synthetic minichromosomes, constructed by reconstituting complexes of core histones with the closed circular plasmid pBR322, were treated with various amounts of DNA gyrase. We have found that the maximum level of supercoiling that is attainable is nearly identical for protein- free plasmids and for plasmids half-saturated with core histones, even though supercoiling does not result in a loss of histones from the complex. It appears that, at sufficiently high levels of supercoiling, contacts between the core particle and DNA are disrupted in such a way that the DNA bound to histones is no longer constrained. Recent experiments indicate that the nucleosome is not opened up into symmetrical halves under these conditions.

在核小体核心粒子中，至少有145个碱基对的DNA