在M阶段和S阶段的ORC的角色
1Division of Genetics, University of California at Berkeley, 401 Barker Hall, Berkeley, CA 94720, USA.
Science (New York, N.Y.)
|March 28, 1998
概括
原始识别复合体 (ORC) 对于酵母中DNA复制的启动至关重要. 突变的Orc5p或Orc2p可以通过抑制复制起源,甚至在存在功能性ORC时,通过抑制复制起源,主要阻止细胞周期进展.
科学领域:
- 分子生物学分子生物学
- 细胞循环规则 细胞循环规则
- 酵母遗传学 酵母遗传学
背景情况:
- 原始识别复合体 (ORC) 在Saccharomyces cerevisiae中启动DNA复制.
- 在细胞周期期间,ORC的组装和激活受到严格的调节,发生在晚期的M和S阶段.
- 特定的ORC子单元,如Orc5p,在不同的细胞周期过渡 (G1/S和M阶段) 中发挥关键作用.
研究的目的:
- 为了研究起源识别复合体 (ORC) 的Orc5p子单元的细胞周期作用.
- 描述ORC子单元中与温度敏感突变相关的表型,特别是ORC5-1和ORC2等位基因.
- 确定在某些ORC突变体中观察到的主导细胞循环停止的机制.
主要方法:
- 利用对温度敏感的酵母突变物 (orc5-1) 来研究ORC功能.
- 采用细胞同步技术 (M相阻断和释放) 来精确地定时细胞周期停止.
- 通过引入野生类型的Orc5p和评估与orc2等位基因相互作用来分析突变表型的优势.
主要成果:
- 对温度敏感的orc5-1突变体表现出不同的细胞周期停止表型,取决于初始同步:异步细胞的早期M阶段和M阶段同步细胞的G1/S边界.
- 由orc5-1引起的G1/S停止在G1.1期间添加野生类型Orc5p并没有被拯救.
- 在orc2和orc5的突变显示出主要的负面影响,抑制细胞循环的进展,这是局部到核.
结论:
- 在酵母中,Orc5p对于通过G1/S和早期M阶段的进展至关重要.
- 突变的ORC复合体,特别是那些涉及Orc2p和Orc5p的复合体,可以对DNA复制启动产生主要的抑制作用.
- 核局部主导抑制表明,突变的ORC复合体会干扰染色体上野生型ORC的功能,阻止功能起源的复制启动.
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02:38S-Cdk Initiates DNA Replication
The cell cycle is a series of events leading to DNA duplication followed by the division of cell content to form two daughter cells. The cell cycle progresses in four stages—the cell increases in size (gap 1 or G1-phase), duplicates its DNA (synthesis or S-phase), prepares to divide (gap 2 or G2-phase), and divides (mitosis or M-phase).
Two states at the origin of replication
In eukaryotes, the initiation of replication occurs at many sites on the chromosomes, called the origins of replication.
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In eukaryotes, the initiation of replication occurs at many sites on the chromosomes, called the origins of replication.
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Checkpoints throughout the cell cycle serve as safeguards and gatekeepers, allowing the cell cycle to progress in favorable conditions and slow or halt it in problematic ones. This regulation is known as the cell cycle control system.
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
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