Developmental regulation of nuclear domains

摘要 在后生动物胚胎中，母体和合子因子合作建立基因调节域，区域 参与基因被协调调控并维持这些结构域的核 在整个发展过程中。为了成功地建立结构域，转录因子必须有效地定位 适当的核区域，在域的上下文中执行正确的功能，并做出贡献 随着受精卵的发育，积极地维持结构域。我们的总体目标是确定核能如何 域名在整个开发过程中都受到监管。定义直接针对域的信号将使我们能够 进一步破译顺式调控密码：蛋白质如何与细胞中的同源序列相互作用，导致 辨证与疾病。 我们将使用果蝇组蛋白基因座来追求这一目标，这是一个高度重复的区域，由 100个串联基因阵列，同时吸引通用和独特的转录因子，形成组蛋白基因座 正文(HLB)域。我们最近描述了组蛋白顺式基因座之间最早的一些相互作用 启动结构域形成的序列和转录因子，但转录因子如何协作 建立和维护一个域没有很好的定义。此外，DNA序列不足以确定 转录因子在一个结构域中发挥作用。相反，因素必须整合多个信息源 序列外，包括基因组背景、染色质提示，如组蛋白标记和三维 轨迹组织，以执行正确的特定于上下文的功能。 捕获导致核域启动的步骤具有挑战性，原因有三：1)许多关键 这些事件发生在非常早期的胚胎中，因为它的细胞很少，因此几乎没有与之相关的生物材料 2)母体沉积的转录因子被加载到卵子中，很难被耗尽；以及3) 在合子基因组激活之前，不可能使用报告转基因。但是，通过使用 异位组蛋白基因阵列，它仍然是结构域形成的靶点，我们可以操纵驻留在 导致转录因子募集的基因座。在我的新实验室里，我们正在使用这个系统， 果蝇中广泛的遗传工具以及克服这些工具的创造性方法 挑战和解决我们在理解胚胎发育过程中核域形成方面的重要差距。 我们将定义启动核域的表观遗传机制，并确定转录因子如何 整合多个级别的基因组信息以执行特定领域的功能。我们的工作意义重大 因为我们的观察将提供对其他重复区域的调节和组织的洞察， 如核糖体RNA基因，以及非基因区域，如端粒和着丝粒。

SUMMARY In metazoan embryos, maternal and zygotic factors collaborate to establish gene regulatory domains, regions of the nucleus in which participating genes are coordinately regulated, and these domains are maintained throughout development. To successfully establish domains, transcription factors must effectively locate the appropriate region of the nucleus, perform the correct function within the context of the domain, and contribute to the active maintenance of the domain as the zygote develops. Our overall goal is to determine how nuclear domains are regulated throughout development. Defining the signals that direct domain targeting will allow us to further decipher the cis regulatory code: how proteins interact with cognate sequences in a cell, leading to differentiation and disease. We will pursue this goal using the Drosophila histone locus, a highly repetitive region composed of over 100 tandem gene arrays that attract both general and unique transcription factors, forming the histone locus body (HLB) domain. We recently described some of the earliest interactions between histone locus cis sequences and transcription factors that initiate domain formation, but how transcription factors collaborate to establish and maintain a domain is not well defined. In addition, DNA sequence is not sufficient to determine transcription factor function within a domain. Rather, factors must integrate multiple sources of information outside of sequence, including genomic context, chromatin cues such as histone marks, and three dimensional locus organization, to perform correct context-specific functions. It is challenging to capture the steps that lead to nuclear domain initiation for three reasons: 1) Many key events take place in the very early embryo which has few cells and therefore little biological material with which to work; 2) Maternally deposited transcription factors are loaded into the egg and are difficult to deplete; and 3) It is not possible to use reporter transgenes before activation of the zygotic genome. However, by using an ectopic histone gene array, which is still targeted for domain formation, we can manipulate signals residing in the locus that lead to transcription factor recruitment. In my new laboratory, we are using this system, the extensive repertoire of genetic tools in Drosophila melanogaster, and creative approaches to overcome these challenges and address important gaps in our understanding of nuclear domain formation during embryogenesis. We will define the epigenetic mechanisms that initiate nuclear domains and determine how transcription factors integrate multiple levels of genomic information to perform domain-specific functions. Our work is significant because our observations will provide insight into the regulation and organization of other repetitive regions, such as the ribosomal RNA genes, as well as for non-genic regions such as telomeres and centromeres.