Accumulation of cyclin E is not a prerequisite for passage through the restriction point
Accumulation of cyclin E is not a prerequisite for passage through the restriction point
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DOI：
10.1128/mcb.21.9.3256-3265.2001
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发表时间：
2001-05-01
影响因子：
5.3
通讯作者：
Zetterberg, A
中科院分区：
文献类型：
--
作者：
Ekholm, SV;Zickert, P;Zetterberg, A
限制点（R）定义为G（1）中的点，在该点之后，细胞可以在没有生长因子的情况下完成分裂周期，并且将G（1）分成两个生理学上不同的周期间隔，G（1）-pm（有丝分裂后间隔，恒定长度为3至4小时）和G（1）-ps（DNA合成前间隔，可变长度为1至10小时）。细胞周期蛋白E是一种G（1）调节蛋白，其积累被认为是通过R的关键。我们研究了异步生长细胞群中单个细胞中细胞周期蛋白E蛋白水平，包括通过R期和进入S期。我们发现，有丝分裂后的G（1）细胞，尚未达到R是阴性的细胞周期素E的积累，另一方面，已通过R的细胞被发现积累细胞周期素E在不同的时间（1至8小时后通过R和2至5小时前进入S）。这些动力学数据排除了通过R通道依赖于细胞周期蛋白E积累的假设，但匡威，表明通过R通道是细胞周期蛋白E积累的先决条件。此外，我们发现大多数细胞周期蛋白E蛋白在进入S后1至2小时内下调。
The restriction point (R) is defined as the point in G(1) after which cells can complete a division cycle without growth factors and divides G(1) into two physiologically different intervals in cycling tells, G(1)-pm (a postmitotic interval with a constant length of 3 to 4 h) and G(1)-ps (a pre-DNA-synthetic interval with a variable length of 1 to 10 h). Cyclin E is a G(1) regulatory protein whose accumulation has been suggested to be critical for passage through R. We have studied cyclin E protein levels in individual cells of asynchronously growing cell populations, with respect to both passage through R and entry into S phase. We found that the postmitotic G(1) cells that had not yet reached R were negative for cyclin E accumulation, On the other hand, cells that had passed R were found to accumulate cyclin E at variable times (1 to 8 h) after passage through R and 2 to 5 h before entry into S. These kinetic data rule out the hypothesis that passage through R is dependent on the accumulation of cyclin E but suggest, instead, the converse, that passage through R is a prerequisite for cyclin E accumulation. Furthermore, we found that most of the cyclin E protein is downregulated within 1 to 2 h after entry into S.