Histone Demethylases and Regulation of Chromatin and Transcription in Eukaryotes

描述(由申请人提供)：组蛋白N末端的共价修饰(磷酸化、乙酰化、泛素化和甲基化)显著影响染色质结构和基因转录。虽然许多这些修饰都是由相反活性的酶动态调节的，但组蛋白甲基化长期以来一直被认为是一种“永久性”的修饰。我们最近发现了第一个组蛋白去甲基酶LSD1(赖氨酸特异性去甲基酶1)，它通过去甲基化组蛋白H3赖氨酸4(H3-K4)来抑制转录，这表明组蛋白甲基化和其他组蛋白修饰一样，也是动态调节的。我们的发现提出了一些重要而令人兴奋的问题。例如，LSD1介导的去甲基化是如何调节的？LSD1的生物学功能是什么？我们的初步发现表明，LSD1相关因子BHC80在调节LSD1介导的H3-K4去甲基化后的染色质事件中具有潜在的非常令人兴奋的作用，并可能与脂质信号有关。研究BHC80调节LSD1的机制是这一应用的重点。为了了解组蛋白去甲基酶的生物学和体内作用机制，我们将分析S.pombe LSD1同源物SPBC146.09C和SPAC23E2.02在常染色质和异染色质生物学中的作用。Pombe异染色质的特征是H3-K9甲基化和H3-K4低甲基化，这与LSD1同源物在异染色质中可能的作用是一致的。通过组蛋白修饰对基因表达的表观遗传调控与包括癌症在内的多种病理条件有关。因此，了解异染色质中的去甲基酶和常染色质基因转录将不仅为染色质生物学提供新的见解，而且将在总体上为细胞增殖控制和肿瘤发生提供新的见解。基于我们令人兴奋的初步结果，拟议的研究可能会导致新的范式，这将显著影响我们对真核细胞染色质和转录调控的看法。

DESCRIPTION (provided by applicant): Covalent modifications (phosphorylation, acetylation, ubiquitination and methylation) of histone N-terminal tails significantly impact chromatin structure and gene transcription. While many of these modifications are regulated dynamically by enzymes of opposing activities, histone methylation has long been considered a "permanent" modification. We have recently discovered the first histone demethylase LSD1 (Lysine Specific Demethylase 1), which represses transcription by demethylating histone H3 lysine 4 (H3-K4), demonstrating that histone methylation, like other histone modifications, is also regulated dynamically. Our findings raise a number of important and exciting questions. For instance, how is LSD1-mediated demethylation regulated? What are the biological functions of LSD1? Our preliminary findings suggest a potentially very exciting role for BHC80, an LSD1 associated factor, in regulating chromatin events post H3-K4 demethylation mediated by LSD1, and a possible connection to lipid signaling. Investigation of mechanisms by which BHC80 regulates LSD1 is a focus of this application. To understand the biology and in vivo mechanism of action of histone demethylases, we will analyze the roles of S. pombe LSD1 homologs, SPBC146.09C and SPAC23E2.02, in both euchromatin and heterochromatin biology. Pombe heterochromatin is characterized by H3-K9 methylation and H3-K4 hypomethylation, which is consistent with a possible role for LSD1 homologs in heterochromatin. Epigenetic regulation of gene expression via histone modifications has been linked to multiple pathological conditions including cancer. Thus, an understanding of demethylases in heterochromatin as well as euchromatin gene transcription will provide new insights not only into chromatin biology but also cell proliferation control and tumorigenesis in general. Based on our exciting initial results, the proposed studies are likely to result in new paradigms that will significantly impact our views of eukaryotic chromatin and transcriptional regulation.