S-PHASE-PROMOTING CYCLIN-DEPENDENT KINASES PREVENT RE-REPLICATION BY INHIBITING THE TRANSITION OF REPLICATION ORIGINS TO A PRE-REPLICATIVE STATE
S-PHASE-PROMOTING CYCLIN-DEPENDENT KINASES PREVENT RE-REPLICATION BY INHIBITING THE TRANSITION OF REPLICATION ORIGINS TO A PRE-REPLICATIVE STATE
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DOI：
10.1016/s0960-9822(95)00252-1
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发表时间：
1995-11-01
期刊：
影响因子：
9.2
通讯作者：
NASMYTH, KA
中科院分区：
文献类型：
--
作者：
DAHMANN, C;DIFFLEY, JFX;NASMYTH, KA
背景：DNA 复制和有丝分裂是由激酶复合物的激活触发的，每个激酶复合物均由细胞周期蛋白和细胞周期蛋白依赖性激酶 (Cdk) 组成。 Cdks 与不同类别的细胞周期蛋白的关联似乎可能指定是否会发生 S 期（复制）或 M 期（有丝分裂）。最近发现，单个 B 型细胞周期蛋白（由基因 CLB1-CLB6 编码）可以在芽殖酵母酿酒酵母的两个过程中发挥功能，这对这一观点提出了质疑。结果：缺乏 Clb1-Clb4 的酿酒酵母菌株只经历一次 DNA 复制，但无法进入有丝分裂。我们在两个基因 SIM1 和 SIM2（SIM2 与 SEC72 相同）中分离出突变，这使得此类细胞能够进行额外一轮的 DNA 复制而无需有丝分裂。促进 S 期的 Clb5 激酶在亲本菌株细胞的 G2 期停滞期间保持活性，但在细胞静止期其活性迅速下降。突变体。 CLB5 ene 表达增加可防止再复制。因此，促进 G1 期细胞中 DNA 复制的细胞周期蛋白 B 激酶可以预防 G2 期细胞中的再复制。通过表达特异性 Clb-Cdk1 抑制剂 p40(SIC1) 使 Clb 激酶失活，足以在被诺考达唑阻断在 G2/M 期的细胞的复制起点处诱导复制前状态。 Clb-Cdk1 激酶的重新激活诱导第二轮 DNA 复制。结论：我们提出 S 期促进细胞周期蛋白 B-Cdk 复合物通过抑制复制起点向复制前状态的转变来防止 S、G2 和 M 期的重新复制。该模型可以解释为什么每个 S 阶段起源仅“触发”一次，以及为什么 S 阶段依赖于前面的 M 阶段的完成。
Background: DNA replication and mitosis are triggered by activation of kinase complexes, each made up of a cyclin and a cyclin-dependent kinase (Cdk). It had seemed possible that the association of Cdks with different classes of cyclins specifies whether S phase (replication) or M phase (mitosis) will occur. The recent finding that individual B-type cyclins (encoded by the genes CLB1-CLB6) can have functions in both processes in the budding yeast Saccharomyces cerevisiae casts doubt on this notion.Results: S, cerevisiae strains lacking Clb1-Clb4 undergo DNA replication once but fail to enter mitosis. We have isolated mutations in two genes, SIM1 and SIM2 (SIM2 is identical to SEC72), which allow such cells to undergo an extra round of DNA replication without mitosis. The Clb5 kinase, which promotes S phase, remains active during the G2-phase arrest of cells of the parental strain, but its activity declines rapidly in sill? mutants. Increased expression of the CLB5 ene prevents re-replication Thus, a cyclin B-kinase that promotes DNA replication in G1-phase cells can pr-event re-replication in G2-phase cells. Inactivation of Clb kinases by expression of the specific Clb-Cdk1 inhibitor p40(SIC1) is sufficient to induce a pre-replicative state at origins of replication in cells blocked in G2/M phase by nocodazole. Re-activation of Clb-Cdk1 kinases induces a second round of DNA replication.Conclusions: We propose that S-phase-promoting cyclin B-Cdk complexes prevent re-replication during S, G2 and M phases by inhibiting the transition of replication origins to a pre-replicative state. This model can explain both why origins 'fire' only once per S phase and why S phase is dependent on completion of the preceding M phase.