A non-canonical role for EZH2 in rRNA methtlation

背景：越来越多的证据表明，失调的表观遗传修饰在人类遗传学中起着至关重要的作用。 癌症的发生、发展和转移。表观遗传调控包括组蛋白修饰、DNA 甲基化和去甲基化，通过microRNA和长链非编码RNA（lncRNA）的调节，以及 RNA甲基化和编辑RNA甲基化发生在所有信使RNA（mRNA）、转移RNA（tRNA） 核糖体RNA（rRNA）与最近在理解mRNA甲基化方面的进展相比， rRNA甲基化的功能研究不足。 表观遗传修饰剂Polycomb组蛋白EZH 2，一种众所周知的致癌组蛋白赖氨酸 H3 K27甲基化的甲基转移酶和多梳抑制复合物2（PRC 2）的关键组分， 在癌症中上调，并且是侵袭性癌症的生物标志物。我们的初步数据显示，EZH 2直接 与FBL（Fibrillarin）相互作用，FBL是唯一表征的rRNA 2 '-O-核糖甲基转移酶，并调节rRNA 2 '-O-甲基化水平。敲低EZH 2改变FBL介导的新生肽合成，IRES驱动 蛋白质翻译起始和其他核糖体功能。重要的是，我们的数据表明，FBL是上调 EZH 2高FBL高PCa患者的临床结局比其他患者差。 目的/假设：我们的总体假设是，EZH 2在PCa中起双重作用，典型的作用 作为组蛋白甲基转移酶，通过直接与FBL相互作用， 调节rRNA甲基化和核糖体功能。此外，这种新的EZH 2功能是 独立于PRC 2复合物及其赖氨酸甲基转移酶活性。EZH 2的过表达 FBL联合应用可促进PCa的进展。 根据我们的初步数据，我们提出了以下具体目标来验证我们的假设。 具体目的1：研究EZH 2如何调节盒C/D snoRNP的组装。 具体目标2：表征EZH 2在rRNA甲基化和蛋白质合成中的非典型功能 通过其与FBL在体外的相互作用合成。 具体目的3：研究EZH 2-FBL相互作用和EZH 2的体内新功能。 影响：这项工作将剖析EZH 2如何通过其典型的 作为H3 K27甲基转移酶起作用，并且在经由FBL的rRNA甲基化中起非典型作用。

Background: Mounting evidence suggests that dysregulated epigenetic modifications play a crucial role in cancer initiation, progression, and metastasis. Epigenetic regulations include histone modifications, DNA methylation and demethylation, regulations through microRNA and long non-coding RNAs (lncRNAs), and RNA methylation and editing. RNA methylation occurs on all messenger RNA (mRNA), transfer RNA (tRNA) and ribosome RNA (rRNA). Compared to the recent advances in understanding mRNA methylation, the function of rRNA methylation is understudied. The epigenetic modifier Polycomb group protein EZH2, a well-known oncogenic histone lysine methyltransferase for H3K27 methylation and a key component of Polycomb Repressive Complex 2 (PRC2), is upregulated in cancer and is a biomarker of aggressive cancers. Our preliminary data show that EZH2 directly interacts with FBL (Fibrillarin), the only characterized rRNA 2’-O-ribose methyltransferase, and regulates rRNA 2’-O-methylation levels. Knocking down EZH2 alters FBL-mediated nascent peptide synthesis, IRES-driven protein translation initiation, and other ribosomal functions. Importantly, our data reveal that FBL is upregulated in PCa, and EZH2highFBLhigh PCa patients had worse clinic outcomes compared to other patients. Objective/Hypothesis: Our overall hypotheses are that EZH2 plays dual roles in PCa, a canonical role as histone methyltransferase and a non-canonical role by directly interacting with FBL and then regulating rRNA methylation and ribosomal functions. Further, this novel EZH2 function is independent of the PRC2 complex and its lysine methyltransferase activity. Overexpression of EZH2 and FBL together will promote PCa progression. Based on our preliminary data, we propose the following specific aims to test our hypotheses. Specific Aim 1: To investigate how EZH2 regulates the assembly of box C/D snoRNP. Specific Aim 2: To characterize the non-canonical functions of EZH2 in rRNA methylation and protein synthesis through its interaction with FBL in vitro. Specific Aim 3: To examine the EZH2-FBL interaction and EZH2’s novel functions in vivo. Impact: This work will dissect how EZH2 performs its dual role in cancer progression through its canonical function as a H3K27 methyltransferase and a non-canonical function in rRNA methylation via FBL.