Groth Anja, Ray-Gallet Dominique, Quivy Jean-Pierre, Lukas Jiri, Bartek Jiri, Almouzni Geneviève
Institute of Cancer Biology, The Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
Mol Cell. 2005 Jan 21;17(2):301-11. doi: 10.1016/j.molcel.2004.12.018.
Maintenance of chromosomal integrity requires tight coordination of histone biosynthesis with DNA replication. Here, we show that extracts from human cells exposed to replication stress display an increased capacity to support replication-coupled chromatin assembly. While in unperturbed S phase, hAsf1 existed in equilibrium between an active form and an inactive histone-free pool, replication stress mobilized the majority of hAsf1 into an active multichaperone complex together with histones. This active multichaperone complex was limiting for chromatin assembly in S phase extracts, and hAsf1 was required for the enhanced assembly activity in cells exposed to replication stress. Consistently, siRNA-mediated knockdown of hAsf1 impaired the kinetics of S phase progression. Together, these data suggest that hAsf1 provides the cells with a buffering system for histone excess generated in response to stalled replication and explains how mammalian cells maintain a critical "active" histone pool available for deposition during recovery from replication stresses.
维持染色体完整性需要组蛋白生物合成与DNA复制紧密协调。在此，我们表明，暴露于复制应激的人类细胞提取物支持复制偶联染色质组装的能力增强。在未受干扰的S期，hAsf1以活性形式和无组蛋白的非活性池之间的平衡状态存在，复制应激将大多数hAsf1与组蛋白一起动员到一个活性多分子伴侣复合物中。这种活性多分子伴侣复合物在S期提取物中对染色质组装具有限制作用，并且hAsf1是暴露于复制应激的细胞中增强的组装活性所必需的。一致地，siRNA介导的hAsf1敲低损害了S期进程的动力学。总之，这些数据表明，hAsf1为细胞提供了一个缓冲系统，用于应对复制停滞产生的组蛋白过量，并解释了哺乳动物细胞如何维持一个关键的“活性”组蛋白池，以便在从复制应激中恢复期间用于沉积。
