STAT3 Acetylation and Deacetylation in Metastasis

描述（由申请人提供）：信号传感器和转录激活因子（STAT）的激活和失活分别由蛋白酪氨酸激酶（即JAK）和蛋白酪氨酸磷酸酶（即SHP-2）活性控制。c端区磷酸化STAT二聚体并转移到细胞核中，与DNA结合进行转录激活。为了获得最大的转录活性，STAT需要与其他核因子相互作用。我们实验室的证据表明，p300/CBP和HDAC家族成员都能够与STAT3形成复合物，但对STAT3依赖的转录产生相反的作用：p300/CBP增强STATS的转录活性，而HDAC家族成员HDAC3在293T细胞中的过表达对阻断STAT3依赖的转录非常有效。因此，p300/CBP和HDAC活性可能在调节STAT3活性中发挥关键作用。最近发现STAT3在调节细胞迁移和肿瘤转移中发挥重要作用，但其机制尚不明确。在这方面，STAT3组成性磷酸化在转移性和非转移性细胞中都被广泛检测到。因此，STAT3似乎需要一个额外的翻译后修饰事件来调节与获得转移表型相关的基因转录。本研究要验证的主要假设是STAT活性分别受HAT和HDAC介导的乙酰化和去乙酰化的控制。进一步推测，组成型STAT3乙酰化可能在转移的发展中起核心作用。为了充分验证这些假设，实验将使用我们的抗体阵列技术，特定基因缺陷和/或下调，以及质谱，以便：(1)探索HAT/HDAC作为STAT3信号复合物的组成部分；(2)检测STAT3二聚化过程中STAT3乙酰化的情况，以及STAT3抗失活/降解的能力；(3)验证体内STAT3乙酰化参与转移相关基因调控，组成型STAT3乙酰化负责转移表型的假设。这些互补的方法将阐明不受控制的STAT3乙酰化/去乙酰化在引起癌细胞侵袭和转移中的作用。

DESCRIPTION (provided by applicant): Signal transducer and activator of transcription (STAT) activation and inactivation are controlled by protein tyrosine kinase (i.e., JAK) and protein tyrosine phosphatase (i.e., SHP-2) activities, respectively. C-terminal region phosphorylated STAT dimerize and translocate into nuclei where it binds to DNA for transcriptional activation. To achieve maximum transcriptional activity, STAT needs to interact with other nuclear factors. Evidence from our laboratory shows that both p300/CBP and HDAC family members are capable of forming complexes with STAT3 but exert opposite effects on STAT3-dependent transcription: while p300/CBP enhances STATS's activity in transcription, overexpression of the HDAC family member HDAC3 in 293T cells was highly effective in blocking STAT3-dependent transcription. Thus, p300/CBP and HDAC activities may play key roles in regulating STAT3 activity. Recently, STAT3 has been found to play an important role in regulating cell migration and tumor metastasis although the mechanism has yet to be determined. In this regard, STAT3 constitutive phosphorylation has been widely detected in both metastatic and non-metastatic cells. Thus, an additional post-translational modification event seems to be required for STAT3 to regulate gene transcription relevant to acquisition of the metastatic phenotype. The overarching hypothesis to be tested in this proposal is that STAT activity is under the control of acetylation and deacetylation mediated by HAT and HDAC, respectively. It is hypothesized further that constitutive STAT3 acetylation may play a central role in development of metastasis. To fully test these hypotheses, experiments will use our antibody array technology, specific gene-deficiency and/or down regulation, and mass-spectroscopy in order to: (1) explore HAT/HDAC as components of STAT3 signaling complex; (2) test STAT3 acetylation in STAT3 dimerization and resisting to inactivation/degradation; and (3) test the hypothesis that STAT3 acetylation plays a role in metastasis-related gene regulation and constitutive STAT3 acetylation is responsible for metastatic phenotype in vivo. These complimentary approaches will elucidate the role of uncontrolled STAT3 acetylation/deacetylation in causing cancer cell invasion and metasasis.