Kabli Azhar F, Ng Irene W, Read Nicholas, Pal Parul, Reimann Julia, Tran Ngat T, Albers Sonja-Verena, Le Tung B K, Barillà Daniela
Department of Biology, University of York, York, United Kingdom.
Department of Molecular Microbiology, John Innes Centre, Norwich, United Kingdom.
Nat Commun. 2025 Jul 22;16(1):6759. doi: 10.1038/s41467-025-61997-3.
Chromosome segregation is a fundamental process in all life forms and requires coordination with genome organization, replication and cell division. The mechanism that mediates chromosome segregation in archaea remains enigmatic. Previously, we identified two proteins, SegA and SegB, which form a minimalist chromosome partition machine in Sulfolobales. Here we uncover patterns and mechanisms that SegAB employ to link chromosome organization to genome segregation. Deletion of the genes causes growth and chromosome partition defects. ChIP-seq investigations reveal that SegB binds to multiple sites scattered across the chromosome, but mainly localised close to the segAB locus in most of the examined archaeal genera. The sites are predominantly present in intragenic regions and enriched in one of the two compartments into which the chromosome folds. We show that SegB coalesces into multiple foci through the nucleoid, exhibiting a biased localisation towards the cell periphery, which hints at potential tethers to the cell membrane. Atomic force microscopy experiments disclose short-range DNA compaction and long-range looping of distant sites by SegB, pointing to a significant role for SegB in chromosome condensation that in turn enables genome segregation. Collectively, our data put forward SegAB as important players in bridging chromosome organization to genome segregation in archaea.
染色体分离是所有生命形式中的一个基本过程，需要与基因组组织、复制和细胞分裂相协调。古菌中介导染色体分离的机制仍然是个谜。此前，我们鉴定出了两种蛋白质，SegA和SegB，它们在硫化叶菌中形成了一个简单的染色体分配机器。在这里，我们揭示了SegAB用于将染色体组织与基因组分离联系起来的模式和机制。基因缺失会导致生长和染色体分配缺陷。染色质免疫沉淀测序（ChIP-seq）研究表明，SegB与分布在染色体上的多个位点结合，但在大多数被检测的古菌属中，主要定位于segAB基因座附近。这些位点主要存在于基因内区域，并富集于染色体折叠形成的两个区室之一。我们发现SegB通过类核聚集成多个焦点，在细胞周边呈现偏向定位，这暗示了其与细胞膜潜在的连接。原子力显微镜实验揭示了SegB对远距离位点的短程DNA压缩和长程环化作用，表明SegB在染色体凝聚中起重要作用，进而实现基因组分离。总体而言，我们的数据表明SegAB是古菌中连接染色体组织与基因组分离的重要参与者。
