The Hsk1(Cdc7) Replication Kinase Regulates Origin Efficiency
The Hsk1(Cdc7) Replication Kinase Regulates Origin Efficiency
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DOI：
10.1091/mbc.e08-06-0645
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发表时间：
2008-12-01
影响因子：
3.3
通讯作者：
Rhind, Nicholas
中科院分区：
文献类型：
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作者：
Patel, Prasanta K.;Kommajosyula, Naveen;Rhind, Nicholas
DNA复制的起源通常是低效的，大多数在不到一半的细胞周期内启动。然而，原产地效率调控的机制和重要性都不明确。在裂变酵母菌中，起始燃烧是随机的，这使我们假设起始无效率和随机性是可扩散的速率限制活化剂的结果。我们发现Hsk1-Dfp1复制激酶（裂变酵母Cdc7-Dbf4同源物）发挥了这样的作用。Hsk1-Dfp1水平的升高或降低会相应提高或降低原产地效率。此外，将Hsk1-Dfp1系在一个起始点附近增加了该起始点的效率，这表明Hsk1-Dfp1的有效局部浓度调节起始点的激活。通过光漂白，我们发现Hsk1-Dfp1在细胞核中是自由扩散的。这些结果支持了一个模型，即复制起点对Hsk1-Dfp1的可及性调节起点效率，并提供了染色质结构和复制时间之间的潜在机制联系。通过控制Hsk1-Dfp1水平，我们发现增加或减少起始点发射率会导致基因组不稳定性的增加，这证明了适当的起始点效率的生物学重要性。
Origins of DNA replication are generally inefficient, with most firing in fewer than half of cell cycles. However, neither the mechanism nor the importance of the regulation of origin efficiency is clear. In fission yeast, origin firing is stochastic, leading us to hypothesize that origin inefficiency and stochasticity are the result of a diffusible, rate-limiting activator. We show that the Hsk1-Dfp1 replication kinase (the fission yeast Cdc7-Dbf4 homologue) plays such a role. Increasing or decreasing Hsk1-Dfp1 levels correspondingly increases or decreases origin efficiency. Furthermore, tethering Hsk1-Dfp1 near an origin increases the efficiency of that origin, suggesting that the effective local concentration of Hsk1-Dfp1 regulates origin firing. Using photobleaching, we show that Hsk1-Dfp1 is freely diffusible in the nucleus. These results support a model in which the accessibility of replication origins to Hsk1-Dfp1 regulates origin efficiency and provides a potential mechanistic link between chromatin structure and replication timing. By manipulating Hsk1-Dfp1 levels, we show that increasing or decreasing origin firing rates leads to an increase in genomic instability, demonstrating the biological importance of appropriate origin efficiency.