类固醇受体辅助活化因子的组蛋白修饰酶活性及其在乳腺癌发生发展中的作用

Dysregulation of histone post-translational modifications (PTMs) has been linked to a number of disease states, including developmental and neurological disorders as well as various types of cancer. Using highly sensitive mass spectrometry, a series of novel histone PTMs have been identified recently. However, the addition/removal and biological implications of these newly identified histone acylations remain to be delineated. SRCs have been intensively studied as the nexus in integrating steroid hormone signaling and growth factor pathways to drive oncogenic transcription programs in breast, endometrial, ovarian, prostate and other cancers. SRCs were reported to possess an intrinsic HAT activity in vitro. However, the HAT activities of SRCs were considered to be relatively weak when compared to CBP/p300, raising a possibility that SRCs enzymatically prefer other histone acylations rather than acetylation. In this study, we will utilize a high content screening assay, immunoblotting and mass spectrometric analysis to explore the histone-modifying activities of SRCs. We will demonstrate further the intrinsical links between the histone-modifying activities and the transcription activation functions of SRCs, and investigate the functional significance of these enzymatic activities in breast cancer carcinogenesis. These findings will expand our current understanding of histone acylations and shed new lights into the mechanistic involvements of SRCs in gene transcription and carcinogenesis. This project will open a new window in targeting SRCs for anti-cancer treatment.

组蛋白翻译后修饰的调控异常与多种疾病的发生有关。近些年来，组蛋白翻译后修饰的种类和数量在不断增加，然而这些新修饰的调控机制及生物学功能尚不明确。类固醇受体辅助活化因子(SRCs)家族蛋白可参与包括雌激素受体在内的多种核受体及其他转录因子对靶基因的调控过程，促进乳腺癌、卵巢癌等多种癌症的发生发展。SRCs曾被报道具有体外组蛋白乙酰转移酶活性，但其活性较弱。本项目拟通过高内涵筛选、免疫印迹配合质谱分析，初步确定SRCs的组蛋白修饰酶活性；并利细胞生物学及分子生物学等手段，进一步阐释SRCs的组蛋白修饰酶活性与其转录活性的内在联系；揭示SRCs酶活性在乳腺癌发生发展中的功能及其分子机制。这些结果对于我们深入理解组蛋白修饰以及SRCs参与的基因转录和肿瘤发生发展过程具有重要意义。该研究将为靶向SRCs的乳腺癌治疗提供新思路及理论依据。

组蛋白翻译后修饰的调控异常与多种疾病的发生有关。近些年来，随着高分辨率质谱技术的应用，组蛋白翻译后修饰的种类和数量在不断增加。研究组蛋白修饰是如何被加上去的，又是如何被去除的是表观遗传学领域的核心课题。类固醇受体辅助活化因子(SRCs)，包括三个主要成员SRC-1、GRIP1及AIB1，可参与包括雌激素受体在内的多种核受体及其他转录因子对靶基因的调控过程，其中，AIB1在乳腺癌中的癌基因功能更被广泛报道。SRCs家族成员一直被认为主要作为骨架蛋白招募其它组蛋白修饰酶或染色质重塑因子而发挥其转录激活功能。尽管SRC-1和AIB1曾被报道具有体外组蛋白乙酰转移酶活性，但其活性较弱且其细胞内作用尚未得到明确认识。本项目揭示了包括AIB1在内的SRCs家族蛋白具有组蛋白丁烯酰化、β-羟丁酰化、丙酰化、丁酰化等多种酰化修饰转移酶活性。我们实验验证了AIB1通过其酰化修饰转移酶活性促进靶基因转录，并进一步促进了乳腺癌细胞的生长增殖和侵袭能力。这些研究结果不仅有助于拓展我们对于新型酰化修饰的认知，也进一步明确了AIB1促进基因转录及乳腺癌的新的作用机制，同时也为寻找新型乳腺癌治疗药物的靶标提供一定的理论依据。