Ribosome Biogenesis and p53 Dependent Cell Cycle Control

描述(由申请者提供)：最近的研究确定了一部小说 核仁蛋白，Bop-1，作为哺乳动物rRNA的重要组成部分 加工机械。显性负性抑制因子基因的诱导表达 BOP 1导致28S和5.8S rRNA成熟受阻，出乎意料的是， 胃肠道的强大细胞周期停滞。值得注意的是，这种细胞周期停滞 依赖于哺乳动物细胞中P53的活性，而不是通过 酵母中类似的rRNA加工块。因此，这些观察结果表明 存在一种哺乳动物特有的、由p53介导的监测机制 监测核仁前核糖体组装作为一种新的细胞周期检查点。 这些令人兴奋的发现提供了一个新的视角来理解 核糖体生物发生在细胞周期调控中的作用 实践中但知之甚少的阻断RNA的化疗药物 综合。 可以设想，这种新的监视机制还可以 识别除rRNA加工之外的其他形式的核仁功能障碍 错误，如“核仁应激”。因此，核仁应激可能受制于细胞 循环检查点控制，类似于DNA损伤和复制错误。在……里面 这项建议，关于这个具有广泛意义的几个问题 到目前为止，尚不清楚的细胞周期调控机制将被阐述。首先，是 P53介导的监测是检测核仁应激和 核糖体前组装中的错误总是会导致GI中的细胞周期受阻吗？ 第二，核仁诱导P53活化的机制是什么？ 压力？第三，假设P53或MDM2可能检测到核仁功能障碍 通过与核仁的相互作用，将测试核糖核蛋白复合体。 第四，与Bop 1区域相互作用的蛋白质对产生 细胞周期停滞信号将被识别和表征。通过这些 我们希望通过研究阐明核仁监视的机制 作为一种新的细胞周期检查点。

DESCRIPTION (provided by applicant): Recent studies have identified a novel nucleolar protein, Bop 1, as an essential component of the mammalian rRNA processing machinery. Inducible expression of a dominant negative inhibitor of Bop 1 leads to' blockade of 28S and 5.8S rRNA maturation, and unexpectedly, a powerful cell cycle arrest at Gi. Remarkably, this cell cycle arrest is dependent on the activities of p53 in mammalian cells and is not observed with a similar rRNA processing block in yeast. Thus, these observations indicate the presence of a mammalian-specific, p53-mediated surveillance mechanism that monitors nucleolar pre-ribosome assembly as a novel cell cycle checkpoint. These exciting findings provide a new perspective on understanding the role of ribosome biogenesis in cell cycle control and may explain the action of widely practiced but poorly understood chemotherapeutic agents that block RNA synthesis. It is possible to envisage that this novel mechanism of surveillance may also recognize other forms of nucleolar dysfunction, in addition to rRNA processing errors, as "nucleolar stress." Thus, nucleolar stress may be subject to cell cycle checkpoint control, analogous to DNA damage and replicative errors. In this proposal, several questions of broad significance regarding this heretofore unknown cell cycle regulatory mechanism will be addressed. First, is p53-mediated surveillance a general mechanism of detecting nucleolar stress and do errors in pre-ribosome assembly always lead to a cell cycle block in Gi? Second, what is the mechanism of p53 activation upon induction of nucleolar stress? Third, the hypothesis that p53 or Mdm2 may detect nucleolar dysfunction through interaction with nucleolar ribonucleoprotein complexes will be tested. Fourth, proteins that interact with a region of Bop 1 critical for generating a cell cycle arrest signal will be identified and characterized. Through these studies we hope to elucidate the mechanism by which nucleolar surveillance functions as a novel cell cycle checkpoint.