The role of HMGN2 in enhancing transcription during prolactin receptor signaling

描述（由申请人提供）：乳腺癌是女性中最常见的癌症，也是女性癌症死亡的第二大原因。肽激素催乳素（PRL）促进正常乳腺组织的生长和成熟，但PRL也有助于乳腺癌的发展。这项应用的长期目标是确定PRL信号的分子介质，这些分子介质可以作为新疗法的靶点。通过结合跨膜PRL受体（PRLr）来传递PRL信号。PRLr通过两种方式从细胞表面传递信号到细胞核，1)激活典型信号通路，2)转运到细胞核。在细胞核中，PRLr促进基因表达，但其机制尚未完全阐明。我们发现核PRLr与染色质修饰蛋白高迁移率组N2 （HMGN2）结合，这对促进prl应答基因的表达也很重要。HMGN2可以介导染色质分解，这可能通过允许转录机制进入启动子DNA来促进基因表达。与介导染色质分解一致，HMGN2已被证明可促进组蛋白乙酰化和染色质凝聚连接体组蛋白H1的移位。封闭的目标将确定HMGN2促进PRL应答基因转录的机制。hmgn2介导的prl应答基因启动子的改变程度，包括组蛋白乙酰化和H1位移，将通过染色质免疫沉淀（ChIP）进行研究。HMGN2促进这种变化的机制，如通过募集组蛋白乙酰转移酶，也将被研究。此外，所附目标将决定HMGN2活性如何被调节。HMGN2似乎受到翻译后乙酰化的调节。模拟或阻止这种修饰的HMGN2突变体将分析其介导染色质分解的能力，并将使用ChIP来鉴定基因启动子处的相关组蛋白修饰。乙酰化HMGN2与PRLr结合的能力也将通过共免疫沉淀来评估。该研究的基本原理是，通过确定HMGN2如何促进转录以及该过程如何被调节，各种蛋白质和过程将被视为新型乳腺癌治疗药物的靶点，以减弱PRLr信号。

DESCRIPTION (provided by applicant): Breast cancer is the most common cancer in women and the second leading cause of cancer death in women. The peptide hormone prolactin (PRL) promotes normal breast tissue growth and maturation, but PRL also contributes to breast cancer development. The long-term goal of this application is to determine molecular mediators of PRL signaling which can serve as targets for novel therapeutics. PRL signals by binding to the transmembrane PRL receptor (PRLr). The PRLr signals from the cell surface to the nucleus in two ways, 1) by activating canonical signaling pathways and 2) by translocating to the nucleus. In the nucleus, the PRLr promotes gene expression, but the mechanism by which it does so has not been fully elucidated. We have shown that nuclear PRLr binds to the chromatin-modifying protein high-mobility group N2 (HMGN2), which is also important in promoting the expression of PRL-responsive genes. HMGN2 can mediate chromatin decompaction, which may promote gene expression by allowing the transcriptional machinery to access the promoter DNA. Consistent with mediating chromatin decompaction, HMGN2 has been shown to promote histone acetylation and displacement of the chromatin-condensing linker histone H1. The enclosed aims will determine the mechanism by which HMGN2 promotes the transcription of PRL- responsive genes. The extent of HMGN2-mediated alterations at the promoters of PRL-responsive genes, including histone acetylation and H1 displacement, will be investigated by chromatin immunoprecipitation (ChIP). The mechanism by which HMGN2 promotes such changes, such as by recruiting histone acetyltransferases, will also be investigated. In addition, the enclosed aims will determine how HMGN2 activity is regulated. HMGN2 appears to be regulated by post-translational acetylation. HMGN2 mutants mimicking or preventing such modification will be analyzed for their ability to mediate chromatin decompaction, which will be investigated using ChIP to identify relevant histone modifications at gene promoters. The ability of acetylated HMGN2 to bind to the PRLr will also be assessed by co-immunoprecipitation. The rationale for the proposed research is that by determining how HMGN2 promotes transcription and how that process is regulated, various proteins and processes will be implicated as targets for novel breast cancer therapeutics to attenuate PRLr signaling. PUBLIC HEALTH RELEVANCE: The proposed research aims to establish the role and regulation of HMGN2 in promoting gene expression, which will provide a mechanistic link between nuclear translocation of the PRLr and breast cancer pathogenesis. Characterization of this novel PRLr signaling pathway will have a positive impact on public health by improving our understanding of breast cancer pathogenesis and by identifying targets for the development of novel breast cancer therapies, which are desperately needed for this common and deadly disease.