Active RB elicits late G1/S inhibition
Active RB elicits late G1/S inhibition
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DOI：
10.1006/excr.2002.5510
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发表时间：
2002-06-10
影响因子：
3.7
通讯作者：
Knudsen, ES
中科院分区：
文献类型：
--
作者：
Angus, SP;Fribourg, AF;Knudsen, ES
视网膜母细胞瘤肿瘤抑制蛋白（RB）被激活/去磷酸化，介导细胞周期抑制，以响应抗噬信号。为了阐明RB在这一关键转变中的作用模式，我们利用了可以诱导表达RB组成型活性等位基因（PSM-RB）的细胞系。正如预期的那样，PSM-RB的诱导，而不是野生型蛋白（WT），抑制了向S期的进展。有充分的文献证明，活性RB抑制E2F报告基因的活性，这一观察结果在诱导PSM-RB后得到证实。此外，活性RB抑制e2f -2介导的细胞周期蛋白E的刺激。相比之下，PSM-RB在介导细胞周期抑制时不影响内源性细胞周期蛋白E的mRNA或蛋白水平。同样，当使用p16ink4a激活内源性RB时，对cyclin E蛋白水平没有观察到的影响。在PSM-RB的存在下，CDK2/cyclin E复合物的形成未被破坏，cyclin E相关激酶的活性保持不变。此外，中心体复制（CDK2/cyclin e依赖性事件）在活性RB的存在下没有改变。总之，这些数据表明，活性RB不会通过抑制cyclin E的表达或活性来阻断G1/S转变。相反，PSM-RB通过协调转录抑制和降解导致细胞周期蛋白a蛋白水平的显著降低。细胞周期蛋白A的衰减与细胞周期抑制有关。这些研究表明，RE通过靶向G1/S过渡阶段的CDK2/cyclin a依赖性事件来抑制细胞周期进程。(C) 2002 Elsevier Science （USA）。
The retinoblastoma tumor suppressor protein (RB) is activated/dephosphorylated to mediate cell cycle inhibition in response to antimitogenic signals. To elucidate the mode of RB action at this critical transition, we utilized cell lines that can be induced to express a constitutively active allele of RB (PSM-RB). As expected, induction of PSM-RB, but not wild-type protein (WT), inhibited progression into S phase. It has been well documented that active RB inhibits E2F reporter activity, and this observation was confirmed upon induction of PSM-RB. Additionally, active RB inhibited E2F-2-mediated stimulation of cyclin E. By contrast, PSM-RB did not affect the mRNA or protein levels of endogenous cyclin E when mediating cell cycle inhibition. Similarly, there was no observable effect on cyclin E protein levels when p16ink4a was utilized to activate endogenous RB. CDK2/cyclin E complex formation was not disrupted and cyclin E-associated kinase activity was retained in the presence of PSM-RB. Additionally, centrosome duplication, a CDK2/cyclin E-dependent event, was not altered in the presence of active RB. Together, these data indicate that active RB does not block the G1/S transition through inhibition of cyclin E expression or activity. In contrast, PSM-RB leads to a dramatic reduction in cyclin A protein levels by coordinate transcriptional repression and degradation. This attenuation of cyclin A protein correlates with cell cycle inhibition. These studies indicate that RE inhibits cell cycle progression by targeting CDK2/cyclin A-dependent events at the G1/S transition to inhibit cell cycle progression. (C) 2002 Elsevier Science (USA).