Project 3: Molecular basis for epigenome homeostasis by histone chaperone and acetyltransferase complexes

摘要 这一建议的目标是通过协调的 组蛋白伴侣和乙酰基转移酶复合体的活性。表观基因组保持在 动态平衡，或表观基因组动态平衡，是适当调节基因表达所必需的。 表观基因组动态平衡的破坏是衰老细胞和与年龄相关的疾病的特征，如 癌症，并伴随着异常的表观遗传调控，通常伴随着组蛋白的丢失， 乙酰化组蛋白的异常沉积和隐蔽转录启动。这项提案将重点放在 两个表观遗传调控系统，组蛋白伴侣和组蛋白乙酰转移酶的协调活性， 它们在维持健康细胞的表观基因组动态平衡方面起着主要作用，并在衰老过程中表现出变化 和衰老的细胞。具体地说，我们将研究Hira/UBN1/CABIN1(Huc)组蛋白伴侣蛋白复合体 它特异性地将H3.3组蛋白变体沉积到染色质中，这是一种不依赖于DNA复制的 以转录偶联方式促进特定靶基因的正常转录程序；以及 酵母组蛋白乙酰转移酶(SAS2/4/5和hMOF)将H4K16乙酰化 (H4K16ac)标记，其升高与细胞老化有关。HUC介导的H3.3沉积和 H4K16ac与衰老细胞密切相关，但与增殖细胞无关。我们还将学习ASF1 组蛋白伴侣(来自萌芽酵母和人类)，它与Rtt109组蛋白合作 芽殖酵母中的乙酰转移酶沉积乙酰化的H3K56组蛋白以促进隐蔽转录 启动，并与人类中的Huc复合体维持表观基因组的动态平衡。最后，我们将发展 H4K16ac和Huc介导的H3.3沉积抑制剂对抗促癌衰老- 相关分泌表型(SASP)。具体目的是(1)确定H3.3的分子基础- Huc特异性沉积和靶向调控衰老细胞基因表达，发展Huc 靶向SASP的抑制剂，(2)确定人MOF(HMOF)对H4K16乙酰化的分子基础 和同源发芽酵母SAS2/4/5复合体，并开发小分子H4K16乙酰化途径 促进细胞健康的抑制剂，以及(3)确定ASF1如何合作的分子基础 Rtt109介导衰老细胞的隐蔽转录启动。这些目标将与伯杰紧密相连 (项目2)、亚当斯(项目1)和张(项目4)，并使用B和C核心，我们预计 这些研究将有助于从分子上理解H4K16乙酰化和H3.3的协同作用 组蛋白沉积在控制衰老和隐蔽转录启动中的作用； 抑制衰老细胞H4K16乙酰化和Huc功能的小分子化合物的研究进展 抑制SASP，促进健康。

Summary The goal of this proposal is to determine the molecular basis for epigenome homeostasis by the coordinated activities of histone chaperone and acetyltransferase complexes. The epigenome is maintained in a state of dynamic equilibrium, or epigenome homeostasis, that is required for appropriately regulated gene expression. A breakdown in epigenome homeostasis is a characteristic of aging cells and age-associated diseases such as cancer, and is accompanied by aberrant epigenetic regulation that is often accompanied by loss of histones, aberrant deposition of acetylated histones and cryptic transcription initiation. This proposal will focus on the coordinated activity of two epigenetic regulatory systems, histone chaperones and histone acetyltransferases, which play major roles in maintaining epigenome homeostasis in healthy cells, and show alterations in aging and senescent cells. Specifically, we will study the HIRA/UBN1/CABIN1 (HUC) histone chaperone complex that specifically deposits the H3.3 histone variant into chromatin in a DNA replication-independent and transcription-coupled manner to promote normal transcriptional programs at specific target genes; and the histone acetyltransferases from yeast and human (Sas2/4/5 and hMOF) that places the H4K16 acetylation (H4K16ac) mark, the elevation of which is correlated with aged cells. HUC-mediated H3.3 deposition and H4K16ac is intimately connected in senescent cells, but not proliferating cells. We will also study the Asf1 histone chaperone (from budding yeast and human), which cooperates with the Rtt109 histone acetyltransferase in budding yeast to deposit acetylated H3K56 histones to promote cryptic transcription initiation, and with the HUC complex in human to maintain epigenome homeostasis. Finally, we will develop H4K16ac and HUC-mediated H3.3 deposition inhibitors to counteract cancer-promoting senescence- associated secretory phenotype (SASP). The specific aims are to (1) Determine the molecular basis for H3.3- specific deposition and targeting by HUC to control gene expression in senescent cells, and develop HUC inhibitors to target SASP, (2) Determine the molecular basis for H4K16 acetylation by the human MOF (hMOF) and orthologous budding yeast Sas2/4/5 complex, and develop small molecule H4K16 acetylation pathway inhibitors to promote cellular healthspan, and (3) Determine the molecular basis for how Asf1 cooperates Rtt109 to mediate cryptic transcription initiation in aging cells. These aims will be tightly connected to Berger (Project 2), Adams (Project 1) and Zhang (Project 4) and use Cores B and C. Together, we anticipate that these studies will lead to a molecular understanding of the concerted roles of H4K16 acetylation and H3.3 histone deposition in control of senescence and aging and cryptic transcription initiation; and to the development of small molecule compounds to inhibit H4K16 acetylation and HUC function in aging cells to inhibit SASP and promote healthspan.