Sap1 is a replication-initiation factor essential for the assembly of pre-replicative complex in the fission yeast Schizosaccharomyces pombe
Sap1 is a replication-initiation factor essential for the assembly of pre-replicative complex in the fission yeast Schizosaccharomyces pombe
复制标题
Sap1 是裂殖酵母裂殖酵母中预复制复合物组装所必需的复制起始因子
DOI：
10.1074/jbc.m116.767806
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发表时间：
2017-04-14
影响因子：
4.8
通讯作者：
Kong, Daochun
中科院分区：
文献类型：
--
作者：
Guan, Ling;He, Peng;Kong, Daochun
真核生物染色体DNA复制起始的中心步骤是在细胞周期的M期晚期和G1期早期组装复制前复合物（pre-replicative complex，pre-RC）。自1973年以来，四种蛋白质或蛋白质复合物，包括细胞分裂控制蛋白6（Cdc 6）/Cdc 18，微小染色体维持蛋白复合物，起源识别复合物（ORC）和Cdt 1，是已知的前RC组分。之前，我们报道了一种非ORC蛋白与粟酒裂殖酵母DNA复制起点ARS 3001的必需元件Δ9结合。在这项研究中，我们确定了非ORC蛋白是Sap 1。与ORC一样，Sap 1在细胞生长周期中与DNA来源结合。但与ORC不同，ORC通过其9个AT钩基序与不对称的富含AT的序列结合，Sap 1优先与5′-（A/T）n（C/G）（A/T）9-10（G/C）（A/T）n-3′（n ≥ 1）的DNA序列结合。我们还发现Sap 1和ORC在物理上相互作用。我们进一步证明了Sap 1是前RC组装所必需的，因为它在将Cdc 18募集到DNA来源中起着至关重要的作用。因此，我们得出结论，Sap 1是一个复制起始因子，直接参与前RC的组装。裂殖酵母中的DNA复制起点被定义为具有两个必需元件，一个与ORC结合，另一个与Sap 1结合。
A central step in the initiation of chromosomal DNA replication in eukaryotes is the assembly of pre-replicative complex (pre-RC) at late M and early G1 phase of the cell cycles. Since 1973, four proteins or protein complexes, including cell division control protein 6 (Cdc6)/Cdc18, minichromosome maintenance protein complex, origin recognition complex (ORC), and Cdt1, are known components of the pre-RC. Previously, we reported that a non-ORC protein binds to the essential element Δ9 of the Schizosaccharomyces pombe DNA-replication origin ARS3001. In this study, we identified that the non-ORC protein is Sap1. Like ORC, Sap1 binds to DNA origins during cell growth cycles. But unlike ORC, which binds to asymmetric AT-rich sequences through its nine AT-hook motifs, Sap1 preferentially binds to a DNA sequence of 5′-(A/T)n(C/G)(A/T)9–10(G/C)(A/T)n-3′ (n ≥ 1). We also found that Sap1 and ORC physically interact. We further demonstrated that Sap1 is required for the assembly of the pre-RC because of its essential role in recruiting Cdc18 to DNA origins. Thus, we conclude that Sap1 is a replication-initiation factor that directly participates in the assembly of the pre-RC. DNA-replication origins in fission yeast are defined by possessing two essential elements with one bound by ORC and the other by Sap1.