Roles of Novel Protein Complexes in Estrogen and Progesterone Receptor Signaling

描述(申请人提供)：雌激素受体-1(ER)和孕激素受体(PR)是配体诱导的转录因子。辅助蛋白，称为辅助激活因子，调节这些因子的转录激活。已有研究表明，共激活因子可促进靶基因的转录，并在多种病理过程中发挥重要作用，如癌症、遗传性疾病、代谢紊乱和炎症等。我们实验室早期的工作发现E6相关蛋白(E6-AP)是类固醇激素受体的共激活因子。为了鉴定E6-AP相互作用蛋白(S)，我们克隆了WW结构域结合蛋白-2(WBP-2)，并发现WBP-2选择性地共激活ER和PR的反式激活功能。WBP-2是一个新的富含多聚脯氨酸(PPXY)基序的蛋白质。WBP-2的PPXY基序已被证明参与转录激活途径。PPXY基序与含有WW结构域的蛋白质相互作用，形成PPXY基序和WW结构域(PPXY-WW)复合体，介导转录刺激。PPXY-WW模块在过去的十年中得到了重视，PPXY-WW复合体在细胞核、细胞通路、生理和病理过程中的许多新角色才刚刚出现。在YES相关蛋白(YAP1)和含有WW结构域的氧化还原酶(WWOX1)等关键调控蛋白上发现了WW结构域。YAP1已被证明是几种转录因子的转录辅助激活因子，也被归类为癌蛋白，而WWOX1已被确定为肿瘤抑制因子。我们的初步数据表明，致癌的YAP1与WBP-2结合可以增强ER和PR信号。这种ER和PR信号的增加被肿瘤抑制基因WWOX1减弱，但这些蛋白调控转录、细胞功能、生长和肿瘤发生的确切机制在很大程度上尚不清楚。为了了解这些蛋白的作用机制及其生理和病理关系，我们假设癌蛋白YAP1的共激活功能依赖于WBP-2，其中WBP-2：YAP1复合体增强ER和PR的反式激活功能，从而导致乳腺肿瘤的发生。我们进一步假设WWOX1通过物理上阻断这种复合体(WBP-2：YAP1)的形成而发挥肿瘤抑制作用，导致它们的协同激活和致癌功能减弱。这一假说将通过以下具体目标得到验证：A)确定WW结构域蛋白YAP1和WWOX1在ER和PR介导的基因转录中的作用；B)破译WBP-2、YAP1和WWOX1调节ER和PR反式激活功能的机制；以及C)确定WBP-2、YAP1和WWOX1在乳腺肿瘤发生中的作用。公共卫生相关性：雌激素和孕激素受体是影响许多生理和病理过程的关键调节蛋白，如生殖、新陈代谢和癌症等。共激活蛋白是调节这些受体蛋白功能的蛋白质，也是不同类型癌症发展的关键角色。鉴于这些事实，了解辅助剂生物学及其作用机制将有助于开发新的治疗方法。

DESCRIPTION (provided by applicant): Estrogen receptor-1 (ER) and progesterone receptor (PR) are ligand-induced transcription factors. Accessory proteins, termed coactivators modulate the transcriptional activation of these factors. It has been shown that coactivators enhance transcription of the target genes and play important roles in diverse pathological processes, such as cancers, inherited genetic diseases, metabolic disorders, and inflammation. Earlier work by our laboratory identified E6-associated protein (E6-AP) as a coactivator of steroid hormone receptors. In an attempt to identify E6-AP-interacting protein(s), we have cloned WW-domain binding protein-2 (WBP-2) and have shown that WBP-2 selectively coactivates the transactivation functions of ER and PR. WBP-2 is a novel polyproline rich (PPXY) motif containing protein. The PPXY motif of WBP-2 has been shown to be involved in transcriptional activation pathways. The PPXY motif interacts with WW-domain containing proteins and form PPXY motif and WW-domain (PPXY-WW) complex and mediates transcription stimulation. The PPXY-WW module has gained prominence in the last decade and many new roles of the PPXY-WW complex in the nucleus, cellular pathways, physiological and pathological processes are just emerging. WW-domains have been observed on several key regulatory proteins like yes associated protein (YAP1) and WW-domain- containing oxidoreductase (WWOX1). YAP1 has been shown to act as transcriptional coactivator for several transcription factors and has also been classified as an oncoprotein, whereas, WWOX1 has been identified as a tumor suppressor. Our preliminary data suggest that oncogenic YAP1 in conjunction with WBP-2 enhances ER and PR signaling. This increased in ER and PR signaling is attenuated by the tumor suppressor WWOX1 but the exact mechanism by which these proteins regulate transcription, cell function, growth and tumorigenesis is largely unknown. In order to understand the mechanism of action of these proteins and their physiological and pathological relevance, we hypothesize that the coactivation functions of oncoprotein YAP1 is dependent on WBP-2 where the WBP-2:YAP1 complex enhances ER and PR transactivation functions resulting in breast tumorigenesis. We further hypothesize that WWOX1 acts as a tumor suppressor by physically blocking the formation of this complex (WBP-2:YAP1) resulting in the attenuation of their coactivation and oncogenic functions. This hypothesis will be test by the following specific aims: A) To determine the role of WW-domain containing proteins, YAP1 and WWOX1 in ER and PR-mediated gene transcription; B) To decipher the mechanism by which WBP-2, YAP1 and WWOX1 regulate ER and PR transactivation functions; and C) To determine the role of WBP-2, YAP1 and WWOX1 in breast tumorigenesis. PUBLIC HEALTH RELEVANCE: Estrogen and progesterone receptors are key regulatory proteins that affect many physiological and pathological processes such as reproduction, metabolism and cancer etc. Coactivators are proteins that regulate the functions of these receptor proteins and are also key players in the development of different types of cancers. Given these facts, the understanding of coactivator biology and their mechanism of action will be useful in developing new therapies.