Molecular mechanisms controlling entry into mitosis

描述（由申请人提供）：单细胞生物体显示出在广泛变化的外部条件下保持相同大小的显著能力。多细胞生物也显示出控制细胞大小的显着能力，因为它们能够产生许多不同大小的不同细胞类型。尽管细胞大小控制的基本重要性，我们知道的细胞大小和细胞生长的分子机制，控制很少。维持特定的细胞大小需要细胞生长和细胞分裂的协调。在裂殖酵母中，Wee 1激酶和Cdc 25磷酸酶是协调细胞生长和G2/M期细胞分裂所必需的。Wee 1磷酸化并抑制细胞周期蛋白依赖性激酶，从而延迟进入有丝分裂，直到达到临界尺寸。Cdc 25去除Wee 1添加的抑制性磷酸盐，从而促进进入有丝分裂。对控制Wee 1和Cdc 25活性的信号传导机制的理解应该为细胞如何感知和维持特定的细胞大小提供重要线索。然而，令人惊讶的是，这些机制在很大程度上是未知的。Wee 1和Cdc 25的芽殖酵母同源物被称为Swel和Mih 1。我们最近的工作表明，Swel和Mih 1是协调细胞生长和细胞分裂在G2/M所必需的，这表明分裂酵母Wee 1和Cdc 25的基本功能在芽殖酵母中是保守的。本提案中描述的实验的目标是使用芽殖酵母中可用的强大实验方法来了解G2/M时细胞生长和细胞分裂的协调。我们将首先表征在正常细胞周期期间和在Swe 1依赖的检查点延迟期间调节Swe 1和Mih 1的分子机制。然后，我们将确定负责调节Swe 1和Mih 1的蛋白质，并确定它们是如何被控制的。我们的长期目标是发现调控Swe 1和Mih 1协调细胞生长和细胞分裂的上游生理信号。对协调细胞生长和细胞分裂的机制的理解可能与癌症有关，因为它们代表了旨在阻断肿瘤细胞生长的药物的潜在靶点。

DESCRIPTION (provided by applicant): Single-celled organisms show a remarkable ability to maintain the same size over widely varying external conditions. Multicellular organisms also show a remarkable ability to control cell size, as they are able to generate many different cell types of different sizes. Despite the fundamental importance of cell size control, we know little about the molecular mechanisms that control cell size and cell growth. Maintenance of a specific cell size requires coordination of cell growth and cell division. In fission yeast, the Wee1 kinase and the Cdc25 phosphatase are required for coordination of cell growth and cell division at G2/M. Wee1 phosphorylates and inhibits cyclin-dependent kinases, thereby delaying entry into mitosis until a critical size has been reached. Cdc25 removes the inhibitory phosphate added by Wee1, thereby promoting entry into mitosis. An understanding of the signaling mechanisms that control the activity of Wee1 and Cdc25 should provide important clues to how cells sense and maintain a specific cell size. Surprisingly, however, these mechanisms are largely unknown. The budding yeast homologs of Wee1 and Cdc25 are called Swel and Mih1. Our recent work has shown that Swel and Mih1 are required for coordination of cell growth and cell division at G2/M, indicating that the basic functions of fission yeast Wee1 and Cdc25 have been conserved in budding yeast. The goal of the experiments described in this proposal will be to use the powerful experimental approaches available in budding yeast to understand coordination of cell growth and cell division at G2/M. We will first characterize the molecular mechanisms that regulate Swe1 and Mih1 during a normal cell cycle and during a Swe1 dependent checkpoint delay. We will then identify proteins responsible for regulation of Swe1 and Mih1 and determine how they are controlled. Our long-term goal is to discover the upstream physiological signals that regulate Swe1 and Mih1 to coordinate cell growth and cell division at G2/M. An understanding of the mechanisms that coordinate cell growth and cell division may be relevant to cancer, since they represent potential targets for drugs aimed at blocking the growth of tumor cells.