Karolinska Institute, Department of Cell and Molecular Biology, Stockholm, Sweden.
Crit Rev Biochem Mol Biol. 2012 Jan-Feb;47(1):1-16. doi: 10.3109/10409238.2011.614593. Epub 2011 Sep 19.
Topology is the study of geometric properties that are preserved during bending, twisting and stretching of objects. In the context of the genome, topology is discussed at two interconnected and overlapping levels. The first focuses the DNA double helix itself, and includes alterations such as those triggered by DNA interacting proteins, processes which require the separation of the two DNA strands and DNA knotting. The second level is centered on the higher order organization of DNA into chromosomes, as well as dynamic conformational changes that occur on a chromosomal scale. Here, we refer to the first level as "DNA topology", the second as "chromosome topology". Since their identification, evidences suggesting that the so called structural maintenance of chromosomes (SMC) protein complexes are central to the interplay between DNA and chromosome topology have accumulated. The SMC complexes regulate replication, segregation, repair and transcription, all processes which influence, and are influenced by, DNA and chromosome topology. This review focuses on the details of the relationship between the SMC complexes and topology. It also discusses the possibility that the SMC complexes are united by a capability to sense the geometrical chirality of DNA crossings.
拓扑学是研究物体在弯曲、扭曲和拉伸过程中保持不变的几何性质的学科。在基因组的背景下，拓扑学在两个相互关联和重叠的层面上进行讨论。第一个层面专注于 DNA 双螺旋本身，包括由 DNA 相互作用蛋白触发的改变，这些过程需要分离两条 DNA 链并形成 DNA 扭结。第二个层面则集中在 DNA 形成染色体的高级组织上，以及在染色体尺度上发生的动态构象变化。在这里，我们将第一个层面称为“DNA 拓扑结构”，将第二个层面称为“染色体拓扑结构”。自它们被发现以来，越来越多的证据表明，所谓的结构性维持染色体（SMC）蛋白复合物是 DNA 和染色体拓扑结构相互作用的核心。SMC 复合物调节复制、分离、修复和转录，所有这些过程都影响着 DNA 和染色体拓扑结构，也受其影响。这篇综述重点介绍了 SMC 复合物与拓扑结构之间的关系细节。它还讨论了 SMC 复合物是否有可能通过感知 DNA 交叉的几何手性来联合起来。
