Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.
Curr Genet. 2020 Oct;66(5):895-899. doi: 10.1007/s00294-020-01076-w. Epub 2020 Apr 16.
Structural maintenance of chromosomes (SMC) complexes are ancient and conserved molecular machines that organize chromosomes in all domains of life. We propose that the principles of chromosome folding needed to accommodate DNA inside a cell in an accessible form will follow similar principles in prokaryotes and eukaryotes. However, the exact contributions of SMC complexes to bacterial chromosome organization have been elusive. Recently, it was shown that the SMC homolog, MukBEF, organizes and individualizes the Escherichia coli chromosome by forming a filamentous axial core from which DNA loops emanate, similar to the action of condensin in mitotic chromosome formation. MukBEF action, along with its interaction with the partner protein, MatP, also facilitates chromosome individualization by directing opposite chromosome arms (replichores) to different cell halves. This contrasts with the situation in many other bacteria, where SMC complexes organise chromosomes in a way that the opposite replichores are aligned along the long axis of the cell. We highlight the similarities and differences of SMC complex contributions to chromosome organization in bacteria and eukaryotes, and summarize the current mechanistic understanding of the processes.
结构维持染色体（SMC）复合物是古老而保守的分子机器，它们在所有生命领域中组织染色体。我们提出，为了使 DNA 能够在细胞内以可及的形式存在，所需的染色体折叠原则在原核生物和真核生物中是相似的。然而，SMC 复合物对细菌染色体组织的确切贡献一直难以捉摸。最近的研究表明，SMC 同源物 MukBEF 通过形成从其伸出 DNA 环的丝状轴向核心来组织和个体化大肠杆菌染色体，类似于有丝分裂染色体形成中凝聚素的作用。MukBEF 的作用及其与伴侣蛋白 MatP 的相互作用，通过将相反的染色体臂（复制子）引导到细胞的不同半部分，也促进了染色体的个体化。这与许多其他细菌中的情况形成对比，在这些细菌中，SMC 复合物以一种方式组织染色体，即相反的复制子沿着细胞的长轴对齐。我们强调了 SMC 复合物对细菌和真核生物中染色体组织的贡献的相似性和差异，并总结了目前对这些过程的机制理解。
