Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Science. 2011 Sep 9;333(6048):1445-9. doi: 10.1126/science.1204697.
Bacterial chromosomes are confined in submicrometer-sized nucleoids. Chromosome organization is facilitated by nucleoid-associated proteins (NAPs), but the mechanisms of action remain elusive. In this work, we used super-resolution fluorescence microscopy, in combination with a chromosome-conformation capture assay, to study the distributions of major NAPs in live Escherichia coli cells. Four NAPs--HU, Fis, IHF, and StpA--were largely scattered throughout the nucleoid. In contrast, H-NS, a global transcriptional silencer, formed two compact clusters per chromosome, driven by oligomerization of DNA-bound H-NS through interactions mediated by the amino-terminal domain of the protein. H-NS sequestered the regulated operons into these clusters and juxtaposed numerous DNA segments broadly distributed throughout the chromosome. Deleting H-NS led to substantial chromosome reorganization. These observations demonstrate that H-NS plays a key role in global chromosome organization in bacteria.
细菌染色体被局限在亚微米大小的核区中。核区相关蛋白（NAPs）促进了染色体的组织，但作用机制仍不清楚。在这项工作中，我们使用超分辨率荧光显微镜，结合染色体构象捕获分析，研究了主要 NAP 在活大肠杆菌细胞中的分布。四种 NAPs——HU、Fis、IHF 和 StpA——在核区中广泛分布。相比之下，作为全局转录沉默因子的 H-NS 则在每个染色体上形成两个紧密的簇，这是由 DNA 结合的 H-NS 通过蛋白氨基末端结构域介导的相互作用进行寡聚化驱动的。H-NS 将受调控的操纵子隔离到这些簇中，并使广泛分布在染色体上的许多 DNA 片段并列。删除 H-NS 会导致染色体的大量重排。这些观察结果表明，H-NS 在细菌的全局染色体组织中起着关键作用。
