细胞有序分裂是生命传播的基础，而DNA复制必须受到精确调控。DNA复制应激是内源性基因组不稳定的主要原因，不仅导致衰老，还导致人类神经病理和癌症发展。对于脊椎动物细胞如何选择和激活复制起源具有重要意义，因为不足的起源激发会导致基因组不稳定和复制起始因子突变导致罕见的人类疾病Meier-Gorlin综合征。起源激活的机制在酵母中已得到充分的表征和重建，然而对高等真核生物中该过程的理解还不平衡。复制起源的激发是由S期激酶（CDKs和DDK）驱动的，并导致复制酶解旋酶的激活和形成双向复制叉。我们从无细胞蛙卵提取物获得的数据表明，在复制起始期间，必需蛋白DONSON用于组装活性复制酶解旋酶（CMG复合物）在起源上的组装。之前的研究已经表明，DONSON在DNA复制过程中是必需的，无论是在人类细胞还是在果蝇中，但其作用机制不明。在这里，我们展示DONSON的存在对于复制起始至关重要，因为它与Cdc45和GINS与Mcm2-7复合物的结合以及解旋酶的激活密切相关。为了发挥这一作用，DONSON与启动因子TopBP1以CDK依赖的方式相互作用。在起始的角色之后，DONSON还参与了DNA复制的延伸阶段中的复制体的组装。最近的研究表明，DONSON的突变会导致Meier-Gorlin综合征；因此，DONSON在复制启动中的新角色为患者的DONSON突变引起的表型提供了解释。 © 2023 作者；《核酸研究》的出版权归牛津大学出版社所有。

Faithful cell division is the basis for the propagation of life and DNA replication must be precisely regulated. DNA replication stress is a prominent endogenous source of genome instability that not only leads to ageing, but also neuropathology and cancer development in humans. Specifically, the issues of how vertebrate cells select and activate origins of replication are of importance as, for example, insufficient origin firing leads to genomic instability and mutations in replication initiation factors lead to the rare human disease Meier-Gorlin syndrome. The mechanism of origin activation has been well characterised and reconstituted in yeast, however, an equal understanding of this process in higher eukaryotes is lacking. The firing of replication origins is driven by S-phase kinases (CDKs and DDK) and results in the activation of the replicative helicase and generation of two bi-directional replication forks. Our data, generated from cell-free Xenopus laevis egg extracts, show that DONSON is required for assembly of the active replicative helicase (CMG complex) at origins during replication initiation. DONSON has previously been shown to be essential during DNA replication, both in human cells and in Drosophila, but the mechanism of DONSON's action was unknown. Here we show that DONSON's presence is essential for replication initiation as it is required for Cdc45 and GINS association with Mcm2-7 complexes and helicase activation. To fulfil this role, DONSON interacts with the initiation factor, TopBP1, in a CDK-dependent manner. Following its initiation role, DONSON also forms a part of the replisome during the elongation stage of DNA replication. Mutations in DONSON have recently been shown to lead to the Meier-Gorlin syndrome; this novel replication initiation role of DONSON therefore provides the explanation for the phenotypes caused by DONSON mutations in patients.© The Author(s) 2023. Published by Oxford University Press on behalf of Nucleic Acids Research.