Institute Jacques Monod (UMR 7592) Paris-Cité University / CNRS, 15 rue Hélène Brion 75013 Paris, CEDEX 13, France.
Paris-Saclay University, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 avenue de la Terrasse 91198 Gif-sur-Yvette, France.
Nucleic Acids Res. 2024 Nov 11;52(20):12324-12333. doi: 10.1093/nar/gkae795.
Replication is initiated bidirectionally in the three domains of life by the assembly of two replication forks at an origin of replication. This is made possible by the recruitment of two replicative helicases to a nucleoprotein platform built at the origin of replication with the initiator protein. The reason why replication is initiated bidirectionally has never been experimentally addressed due to the lack of a suitable biological system. Using genetic and genomic approaches, we show that upon depletion of DciA, replication is no longer initiated bidirectionally at the origin of replication of Vibrio cholerae chromosome 1. We show that following unidirectional replication on the left replichore, nascent DNA strands at ori1 anneal to each other to form a double-stranded DNA end. While this DNA end can be efficiently resected in recB+ cells, only a few cells use it to trigger replication on the right replichore. In most DciA-depleted cells, chromosome 1 is degraded leading to cell death. Our results suggest that DciA is essential to ensuring bidirectional initiation of replication in bacteria, preventing a cascade of deleterious events following unidirectional replication initiation.
在生命的三个领域中，复制是通过在复制起点处组装两个复制叉来双向启动的。这是通过将两个复制解旋酶募集到在复制起点处用起始蛋白构建的核蛋白平台上实现的。由于缺乏合适的生物系统，复制为什么要双向起始的问题从未在实验上得到解决。通过遗传和基因组方法，我们表明，在 V. cholerae 染色体 1 的复制起点耗尽 DciA 后，复制不再双向起始。我们表明，在左侧复制叉上进行单向复制后，ori1 处的新生 DNA 链彼此退火形成双链 DNA 末端。虽然这种 DNA 末端在 recB+细胞中可以被有效切除，但只有少数细胞使用它来触发右侧复制叉上的复制。在大多数 DciA 耗尽的细胞中，染色体 1 被降解导致细胞死亡。我们的结果表明，DciA 对于确保细菌中复制的双向起始至关重要，防止了在单向复制起始后发生一连串有害事件。
