Developmental activation of the Rb-E2F pathway and establishment of cell cycle-regulated cyclin-dependent kinase activity during embryonic stem cell differentiation
Developmental activation of the Rb-E2F pathway and establishment of cell cycle-regulated cyclin-dependent kinase activity during embryonic stem cell differentiation
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DOI：
10.1091/mbc.e04-12-1056
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发表时间：
2005-04-01
影响因子：
3.3
通讯作者：
Dalton, S
中科院分区：
文献类型：
--
作者：
White, J;Stead, E;Dalton, S
为了了解早期发育中的细胞周期控制机制以及它们在分化过程中的变化，我们使用胚胎干细胞来模拟胚胎事件。我们的结果表明，随着多能细胞的分化，G(1)期的长度显著增加。在分子水平上，这与细胞周期蛋白依赖性激酶(CDK)复合体的大小发生显著变化、细胞周期调控的CDK2活性的建立以及Rb-E2F功能通路的激活有关。CDK2活性从结构性到细胞周期依赖性的转变与细胞周期中细胞周期蛋白A2和E1蛋白水平的时间变化相吻合。转录机制支持细胞周期蛋白水平的下调及其在分化过程中周期性的建立。随着多能细胞的分化和pRB/p107的活性依赖于细胞周期，E2F-pRB通路被激活，并对E2F靶基因施加细胞周期调节的转录控制，如细胞周期蛋白EL。这些结果表明，CDK2存在一个反馈环，其中CDK2通过调节Cyclin E1转录来控制自己的活动。因此，细胞分裂速率、细胞周期结构的变化以及细胞周期调控的CDK2活性的建立可以通过激活E2F-PRB途径来解释。
To understand cell cycle control mechanisms in early development and how they change during differentiation, we used embryonic stem cells to model embryonic events. Our results demonstrate that as pluripotent cells differentiate, the length of G(1) phase increases substantially. At the molecular level, this is associated with a significant change in the size of active cyclin-dependent kinase (Cdk) complexes, the establishment of cell cycle-regulated Cdk2 activity and the activation of a functional Rb-E2F pathway. The switch from constitutive to cell cycle-dependent Cdk2 activity coincides with temporal changes in cyclin A2 and E1 protein levels during the cell cycle. Transcriptional mechanisms underpin the down-regulation of cyclin levels and the establishment of their periodicity during differentiation. As pluripotent cells differentiate and pRb/p107 kinase activities become cell cycle dependent, the E2F-pRb pathway is activated and imposes cell cycle-regulated transcriptional control on E2F target genes, such as cyclin El. These results suggest the existence of a feedback loop where Cdk2 controls its own activity through regulation of cyclin E1 transcription. Changes in rates of cell division, cell cycle structure and the establishment of cell cycle-regulated Cdk2 activity can therefore be explained by activation of the E2F-pRb pathway.