The Function of PNUTS (Phosphatase Nuclear Targeting Subunit) in the Cell Cycle

描述（由申请人提供）：在癌细胞中，分裂和复制在没有信号的情况下发生。许多控制细胞分裂的蛋白质参与癌症的发展。肿瘤抑制蛋白视网膜母细胞瘤（Rb）的活性通常在癌细胞中失调。Rb抑制其处于活性状态的细胞的增殖，但当其处于非活性状态时允许细胞增殖。Rb活性受其磷酸化状态控制，磷酸化状态受细胞周期蛋白依赖性激酶（cdks）和蛋白磷酸酶1（PP 1）调节。PP1活性由靶向亚基控制，该亚基结合并引导PP1至特定底物。有一个新发现的PP1靶向亚基称为PNUTS（磷酸酶核靶向亚基），它在体外抑制PP1对Rb的活性。PNUTS蛋白在两种类型的乳腺癌细胞中高度表达，因此本项目的具体目的是阐明PNUTS在细胞周期控制中的功能和调控。为了研究PNUTS在细胞分裂周期中的作用，我们打算使用RNA干扰（RNAi）来阻断PNUTS在乳腺癌细胞中的表达，并检测其对PP1酶活性、Rb磷酸化状态和细胞增殖的影响。此外，PNUTS活性的磷酸化调节及其与PP1的关联将被研究。阐明PNUTS在细胞分裂周期中的功能将为细胞增殖的控制和调节提供见解。在癌症中，细胞以不受控制的方式分裂和增殖。因此，对控制细胞分裂的分子的研究可能会导致了解癌细胞发育和生长所需的信息。该项目旨在研究一种名为PNUTS的蛋白质的功能，该蛋白质被认为是乳腺癌细胞增殖的激活剂。

DESCRIPTION (provided by applicant): In cancer cells, division and replication occurs in the absence of signals to do so. Many proteins that control cell division are involved in cancer development. The activity of the tumor suppressor protein, Retinoblastoma (Rb), is often deregulated in cancer cells. Rb inhibits proliferation in cells in which it is active, but allows cell proliferation when it is inactive. Rb activity is controlled by its phosphorylation state which is regulated by cyclin dependent kinases (cdks) and Protein phosphatase 1 (PP1). PP1 activity is controlled by targeting subunits that bind to and direct it to specific substrates. There is a newly identified PP1-targeting subunit called PNUTS (Phosphatase Nuclear Targeting Subunit) which inhibits PP1 activity toward Rb in vitro. The PNUTS protein is highly expressed in two types of breast cancer cells, therefore the specific aims of this project are designed to elucidate the function of and regulation of PNUTS in cell cycle control. To investigate the role of PNUTS in the cell division cycle, we intend to use RNA interference (RNAi) to block PNUTS expression in breast cancer cells and examine the effects on the enzyme activity of PP1, Rb phosphorylation status and cell proliferation. In addition, the regulation of PNUTS activity by phosphorylation and its association with PP1 will be investigated. The elucidation of PNUTS function in the cell division cycle will provide insight into the control and regulation of cell proliferation. In cancer, cells divide and proliferate in an uncontrolled manner. Thus, the investigation of the molecules that control cell division may lead to information needed to understand cancer cell development and growth. This project is designed to study the function of a protein called PNUTS which is proposed to be an activator of cell proliferation in breast cancer.