Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
Genome Integrity and Cancer UMR 9019 CNRS, Université Paris Saclay, Gustave Roussy, 114 Rue Edouard Vaillant, 94805 Villejuif, France.
Int J Mol Sci. 2023 Jan 11;24(2):1427. doi: 10.3390/ijms24021427.
DciA is the ancestral bacterial replicative helicase loader, punctually replaced during evolution by the DnaC/I loaders of phage origin. DnaC helps the helicase to load onto DNA by cracking open the hexameric ring, but the mechanism of loading by DciA remains unknown. We demonstrate by electron microscopy, nuclear magnetic resonance (NMR) spectroscopy, and biochemistry experiments that DciA, which folds into a KH-like domain, interacts with not only single-stranded but also double-stranded DNA, in an atypical mode. Some point mutations of the long α-helix 1 demonstrate its importance in the interaction of DciA for various DNA substrates mimicking single-stranded, double-stranded, and forked DNA. Some of these mutations also affect the loading of the helicase by DciA. We come to the hypothesis that DciA could be a DNA chaperone by intercalating itself between the two DNA strands to stabilize it. This work allows us to propose that the direct interaction of DciA with DNA could play a role in the loading mechanism of the helicase.
DciA 是细菌复制解旋酶的古老加载器，在进化过程中被噬菌体起源的 DnaC/I 加载器准确替代。DnaC 通过打开六聚体环帮助解旋酶加载到 DNA 上，但 DciA 的加载机制仍不清楚。我们通过电子显微镜、核磁共振（NMR）光谱和生化实验证明，折叠成 KH 样结构域的 DciA 不仅与单链 DNA 而且与双链 DNA 以非典型模式相互作用。长 α 螺旋 1 的某些点突变表明其在 DciA 与模拟单链、双链和分叉 DNA 的各种 DNA 底物相互作用中的重要性。这些突变中的一些也会影响 DciA 对解旋酶的加载。我们提出假设，DciA 可以通过插入双链 DNA 之间来充当 DNA 伴侣，从而稳定双链 DNA。这项工作使我们能够提出 DciA 与 DNA 的直接相互作用可能在解旋酶的加载机制中发挥作用。
