Cell cycle regulation of the licensing activity of Cdt1 in Xenopus laevis
Cell cycle regulation of the licensing activity of Cdt1 in Xenopus laevis
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DOI：
10.1016/j.yexcr.2003.11.018
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发表时间：
2004-04-15
影响因子：
3.7
通讯作者：
Méchali, M
中科院分区：
文献类型：
--
作者：
Maiorano, D;Rul, W;Méchali, M
CDT1是一种保守的复制因子，在单轮DNA合成的染色体许可中是必需的。Cdt1的活性被人参皂苷抑制。双黄素干扰CDT1活性的机制尚不清楚。据认为，双黄素与CDT1结合并隔离。我们表明，双黄素不干扰CDT1的染色质结合，并且观察到双黄素在染色质上积累后对DNA合成的抑制。在S期研究了双黄素与染色质的结合。我们证明了将双黄素加载到染色质上需要CDT1，这表明双黄素的靶点是复制起点。我们还发现，在从复制前复合体到起始前复合体的转变过程中，双黄素与染色质结合，这与CDT1的释放重叠。这种调节与在体细胞中观察到的显著不同，在体细胞中，这些蛋白质的染色质结合是相互排斥的。与体细胞相比，我们进一步证明双黄素在早期胚胎细胞周期中是稳定的。这些结果表明，原始激发的特定调节适应于非洲爪哇快速的细胞周期，并表明在胚胎发育过程中，双黄素的周期性降解与许可无关。(C)2004 Elsevier Inc.保留所有权利。
Cdt1 is a conserved replication factor required in licensing the chromosome for a single round of DNA synthesis. The activity of Cdt1 is inhibited by geminin. The mechanism by which geminin interferes with Cdt1 activity is unknown. It is thought that geminin binds to and sequestrate Cdt1. We show that geminin does not interfere with the chromatin association of Cdt1 and that inhibition of DNA synthesis by geminin is observed following its accumulation on chromatin. The binding of geminin to chromatin has been investigated during S phase. We demonstrate that loading of geminin onto chromatin requires Cdt1, suggesting that geminin is targeted at replication origins. We also show that geminin binds chromatin at the transition from the pre-replication to pre-initiation complexes, which overlaps with the release of Cdt1. This regulation is strikingly different from that observed in somatic cells where the chromatin binding of these proteins is mutually exclusive. In contrast to somatic cells, we further show that geminin is stable during the early embryonic cell cycles. These results suggest a specific regulation of origin firing adapted to the rapid cell cycles of Xenopus and indicate that periodic degradation of geminin is not relevant to licensing during embryonic development. (C) 2004 Elsevier Inc. All rights reserved.