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首页> 外文期刊>Current Biology: CB >Developmental Control of Late Replication and S Phase Length
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Developmental Control of Late Replication and S Phase Length

机译：后期复制和S相长度的发展控制

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Background: Fast, early embryonic cell cycles have correspondingly fast S phases. In early Drosophila embryos, forks starting from closely spaced origins replicate the whole genome in 3.4 min, ten times faster than in embryonic cycle 14 and a hundred times faster than in a wing disc. It is not known how S phase duration is regulated. Here we examined prolongation of embryonic S phases, its coupling to development, and its relationship to the appearance of heterochromatin.Results: Imaging of fluorescent nucleotide incorporation and GFP-PCNA gave exquisite time resolution of S phase events. In the early S phases, satellite sequences replicated rapidly despite a compact chromatin structure. In S phases 11-13, a delay in satellite replication emerged in sync with modest and progressive prolongation of S phase. In S phase 14, major and distinct delays ordered the replication of satellites into a sequence that occupied much of S phase. This onset of late replication required transcription. Satellites only accumulated abundant heterochromatin protein 1 (HP1) after replicating in S phase 14. By cycle 15, satellites clustered in a compact HP1-positive mass, but replication occurred at decondensed foci at the surface of this mass.Conclusions: The slowing of S phase is an active process, not a titration of maternal replication machinery. Most sequences continue to replicate rapidly in successive cycles, but increasing delays in the replication of satellite sequences extend S phase. Although called constitutively heterochromatic, satellites acquire the distinctive features of heterochromatin, compaction, late replication, HP1 binding, and aggregation at the chromocenter, in successive steps coordinated with developmental progress.
机译：背景：快速，早期的胚胎细胞周期具有相应的快速S期。在早期的果蝇胚胎中，从紧密间隔的起源开始的叉子在3.4分钟内复制了整个基因组，比胚胎周期14快十倍，比翅片快一百倍。尚不知道如何调节S相持续时间。在这里，我们检查了胚胎S期的延长，其与发育的耦合以及与异染色质外观的关系。结果：荧光核苷酸掺入和GFP-PCNA的成像提供了S期事件的精确时间分辨率。在早期的S阶段，尽管染色质结构紧凑，但卫星序列却迅速复制。在S期11-13，卫星复制的延迟与S期的适度和逐步延长同步出现。在S期14中，主要和明显的延迟命令将卫星复制到一个占用S期大部分时间的序列中。晚期复制的这种发作需要转录。卫星在S期14中复制后仅积累了丰富的异染色质蛋白1（HP1）。到第15个周期，卫星聚集在一个紧凑的HP1阳性团块中，但复制发生在该团块表面的缩合焦点上。结论：S的减慢阶段是一个活跃的过程，而不是滴定母体复制机制。大多数序列在连续的周期中继续快速复制，但是卫星序列复制中不断增加的延迟延长了S期。尽管称为组成性异色，但卫星在与开发进度相协调的连续步骤中具有异染色质，紧实，后期复制，HP1结合和在色中心聚集的独特特征。

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