Hormone Receptor Regulation of RNA Polymerase III

项目总结 类固醇受体是核受体(NR)转录因子的一个子集，仅在脊椎动物中发现 并调节机体发育和繁殖等基本功能，同时也影响衰老， 肿瘤发生和癌症进展。小分子亲脂激素与雌激素的类固醇受体结合 α和ER-β)、孕酮(PR)、糖皮质激素(GR)和雄激素(AR)并传递它们的信号 通过基因调控。由于这些小分子可以被人工修饰和制造，因此有各种 的药物为新陈代谢障碍、生殖和其他疾病提供关键药物 癌症治疗。NR的作用机制主要是在转录的RNA聚合酶II(POL II)上研究的 基因包括编码蛋白质的mRNAs和小/长的非编码rna。多个核受体作用于DNA上的复合体 激活或抑制POL II转录。然而，NR控制的细胞转录本通常并不总是紧密的 与蛋白质组相关的是由于转录后调控，但尚未完全了解。我们有 通过调节RNA聚合酶III发现了第二层协调的NR活性(POL III) 转录的基因。POL III转录小RNA，是将mRNAs翻译成包括tRNAs在内的蛋白质所必需的 和5S rRNA，是控制细胞生长、干细胞、衰老和癌症的主要节点。负调控 Pol III的表达通常是通过保守的抑制因子Maf1实现的。关于NRS是如何监管的，人们知之甚少 POL III在更复杂的哺乳动物细胞和生物体中。我们发现通过对PR的全基因组分析 ER+PR+乳腺癌细胞系和PR定位于多个tRNA基因的肿瘤中的染色质结合。印刷机 与POL III复合体结合，降低tRNA水平和蛋白质合成。黄体酮招募公关 和维甲酸受体α(RARDNA)到tRNA基因的保守序列附近，类似于NR 结合半个位点。我们的假设是，PR通过与Pol III的串扰来调节tRNA基因的转录 RARtRNA和Maf1的招募导致靶α基因水平下降和选择性翻译。目标 1将确定PR如何与tRNA基因相关联，RARα和其他类固醇受体的作用，以及NR 结合半个位点。目的2确定Maf1在PR调控Pol III转录中的作用。目标3将定义 激素诱导的tRNA池的变化及其对翻译效率的影响。对POL III的监管是 与POL II相比，研究很少，对正常和致癌细胞表型至关重要。这样做的结果是 研究将在PolIII基因上定义一种新的NR作用机制，这将有助于解释i)额外的一层 有助于选择性mRNA翻译的激素调节，以及ii)NRs如何汇聚到多个细胞上 影响细胞生长、分化、干性和肿瘤进展的聚合酶。

Project summary Steroid receptors are a subset of nuclear receptor (NR) transcription factors that are found only in vertebrates and regulate essential functions such as organismal development and reproduction, while also impacting aging, tumorigenesis, and cancer progression. Small lipophilic hormones bind to steroid receptors for estrogens (ER- alpha and ER-beta), progesterone (PR), glucocorticoids (GR), and androgens (AR) and transmit their signal through gene regulation. Since these small molecules can be synthetically modified and manufactured, a variety of pharmaceutical drugs provide critical medicines for diseases including metabolic disorders, reproduction, and cancer treatment. NR mechanism of action has been mostly studied at RNA polymerase II (Pol II) transcribed genes including protein-coding mRNAs and small/long non-coding RNAs. Multiple NRs act in complexes on DNA to activate or repress Pol II transcription. However, NR controlled cell transcriptomes are often not always tightly correlated with the proteome due to post-transcriptional regulation that is not completely understood. We have uncovered a second layer of coordinated NR activity through regulation of RNA Polymerase III (Pol III) transcribed genes. Pol III transcribes small RNAs essential for translation of mRNAs into protein including tRNAs and 5S rRNA and is a major node for controlling cell growth, stem cells, aging, and cancer. Negative regulation of Pol III is commonly through the conserved repressor Maf1. Very little is known concerning how NRs regulate Pol III in more complex mammalian cells and organisms. We discovered using genome-wide analyses of PR chromatin binding in ER+PR+ breast cancer cell lines and tumors that PR localizes at multiple tRNA genes. PR associates with the Pol III complex and decreases tRNA levels and protein synthesis. Progesterone recruits PR and retinoic acid receptor alpha (RARα) to tRNA genes near a conserved DNA sequence resembling an NR binding half site. Our hypothesis is that PR regulates Pol III transcription of tRNA genes through crosstalk with RARα and recruitment of Maf1 resulting in decreased levels of target tRNA genes and selective translation. Aim 1 will determine how PR associates at tRNA genes, the role of RARα and other steroid receptors, and the NR binding half site. Aim 2 will determine the role of Maf1 in PR modulation of Pol III transcription. Aim 3 will define hormone-induced changes in the tRNA pool and the impact on translational efficiency. Regulation of Pol III is vastly understudied compared to Pol II and crucial for normal and oncogenic cell phenotypes. Results of this study will define a novel mechanism of NR action at Pol III genes that will help explain i) an additional layer of hormone regulation that contributes to selective mRNA translation, and ii) how NRs converge on multiple cell polymerases to impact cell growth, differentiation, stemness, and tumor progression.