Chromatin PTEN: Its Regulation And Functions

染色质PTEN的调控与功能 磷酸酶和张力蛋白同源物（PTEN）作为PI 3 K信号传导的主要负调节物发挥作用 通路PTEN在多种人类恶性肿瘤中频繁突变，包括胶质母细胞瘤、前列腺癌、乳腺癌 癌症和乳腺癌。遗传性PTEN突变导致癌症易感性条件。PTEN也是 已知具有核/染色质功能，其失调明显导致染色体不稳定。 然而，染色质PTEN的确切功能及其分子调控仍然知之甚少。过去 研究表明，基因毒性应激后PTEN的适当亚细胞定位受分子调控， 涉及翻译后修饰的机制。我们最近证明，染色质PTEN 在有丝分裂期间显著增加，与C-末端中PTEN磷酸化的增加一致。 尾巴生物化学和分子分析显示Plk 1负责PTEN磷酸化， S380，不被任何其他已知激酶靶向的残基。我们和其他人已经表明，PTEN特异性地 与两种泛素E3连接酶Cdh 1（APC/CCDh 1）和WWP 2相互作用。有丝分裂期间染色质PTEN的去除 PTEN与Cdh 1之间的物理相互作用是一个依赖于蛋白酶体的过程。 此外，我们观察到WWP 2的切割形式在G2和有丝分裂阶段特异性富集， 与染色质PTEN积累相关。WWP 2沉默加速有丝分裂进程。我们 假设染色质PTEN在有丝分裂进程中起着至关重要的作用， Plk 1、Cdh 1和WWP 2控制着细胞的定位和功能， 导致染色体不稳定和肿瘤发展。为了验证我们的假设，我们将 确定磷酸化是否以及如何促进PTEN的染色质易位，剖析 PTEN泛素E3连接酶在调节其稳定性方面的作用，并研究了PTEN的磷酸酶非依赖性功能 在抑制染色体不稳定性和肿瘤的发展使用在体内和体外模型。我们 拟议的研究不仅将阐明染色质PTEN受调控的分子机制， 在细胞周期中，但也将揭示如何PTEN功能，在维持染色体的稳定性， 抑制恶性转化。这一系列的研究可以导致新分子的鉴定， PTEN调控网络中的靶点，可用于癌症药物设计和开发。

Chromatin PTEN: Its Regulation And Function Phosphatase and tensin homolog (PTEN) functions as a major negative regulator of the PI3K signaling pathway. PTEN is frequently mutated in a variety of human malignancies including glioblastoma, prostate cancer, and breast cancer. Inherited PTEN mutations cause cancer-susceptibility conditions. PTEN is also known to have nuclear/chromatin functions, deregulation of which apparently causes chromosomal instability. However, the exact functions of chromatin PTEN and its molecular regulation remain poorly understood. Past research shows that proper subcellular localization of PTEN after genotoxic stress is regulated by molecular mechanisms that involve post-translational modifications. We recently demonstrated that chromatin PTEN significantly increases during mitosis, coinciding with an increase in PTEN phosphorylation in the C-terminal tail. Biochemical and molecular analyses revealed that Plk1 was responsible for PTEN phosphorylation on S380, a residue not targeted by any other known kinases. We and others have shown that PTEN specifically interacts with Cdh1 (APC/CCdh1) and WWP2, two ubiquitin E3 ligases. Chromatin PTEN removal during mitotic exit and the physical interaction between PTEN and Cdh1 was a proteasome-dependnent process. Furthermore, we observed that a cleaved form of WWP2 specifically is enriched during G2 and mitotic stages, correlating with chromatin PTEN accumulation. WWP2 silencing accelerates mitotic progression. We hypothesize that chromatin PTEN plays a crucial role in mitotic progression, whose subcellular localization and function are controlled by Plk1, Cdh1 and WWP2, and that its molecular deregulation leads to chromosomal instability and tumor development. To test the validity of our hypothesis, we will determine whether and how phosphorylation facilitates chromatin translocation of PTEN, dissect the role of PTEN ubiquitin E3 ligases in regulating its stability, and study the phosphatase-independent function of PTEN in supressing chromosomal instability and tumor development using both in vivo and in vitro models. Our proposed studies will not only elucidate the molecular mechanism by which chromatin PTEN is regulated during the cell cycle, but will also reveal how PTEN functions in maintaining chromosomal stability and suppressing malignant transformation. This line of research can lead to the identification of new molecular targets in the PTEN regulatory network that can be explored for cancer drug designs and development.