Developmental Gene Regulation Via Chromatin Remodeling

描述(由申请人提供)：在发育过程中，差异基因表达控制着建立模式形成和器官发生所需的细胞多样性的产生。在整个发育过程中确保适当的时间和空间基因表达的一个重要机制是在转录水平上的调控。转录调控是一个高度动态的细胞过程，涉及一系列复杂的蛋白质-蛋白质和蛋白质-DNA相互作用。对酵母(酿酒酵母)和果蝇(黑腹果蝇)的研究涉及到许多调控蛋白，包括通用的和基因特异性的，以及这一过程中不可或缺的调控机制。转录调控的关键因子类是那些调节染色质结构的因子。染色质重塑是至关重要的，因为它影响核小体的构象和位置，如果核小体位于启动子元件上，可以阻止RNA聚合酶II全酶访问DNA并启动转录。哺乳动物SWI/SNF相关复合体利用Brahma(BRM)或Brahma相关基因1(Brg1)催化亚基以ATP依赖的方式重塑核小体。Brg1零突变被产生，纯合子在植入时死亡，但由于Brgi mRNA和蛋白在卵母细胞中高水平表达，已经设计了实验来确定合子基因组激活是否需要Brg1。Brg1是两个不同但相关的染色质重塑复合体的催化亚单位，这一事实也使围植入期表型的解释变得复杂。因此，缺乏复合体特定亚基的小鼠将被创造出来，以评估每个复合体的相对重要性。最后，为了超越植入和阐明Brg1在胚胎和出生后发育的后期阶段的功能，正在使用ENEJ突变和Cre-loxP条件基因打靶来检测它在造血系统发育中的作用。

DESCRIPTION (provided by applicant): During development, differential gene expression governs generation of the cellular diversity required for establishment of pattern formation and organogenesis. An important mechanism to ensure proper temporal and spatial gene expression throughout development is regulation at the transcriptional level. Regulation of transcription is a highly dynamic cellular process involving a complex array of protein-protein and protein-DNA interactions. Studies in yeast (Saccharomyces cerevisiae) and fruit fly (Drosophila melanogaster) implicate a number of regulatory proteins, both general and gene-specific, as well as regulatory mechanisms integral to this process. Key classes of factors in transcriptional regulation are those that modulate chromatin structure. Chromatin remodeling is of fundamental importance because it affects the conformation and position of nucleosomes, which, if situated at promoter elements, can prevent RNA polymerase II holoenzyme from accessing DNA and initiating transcription. Mammalian SWI/SNF-related complexes utilize either brahma (Brm) or brahma-related gene 1 (Brgl) catalytic subunits to remodel nucleosomes in an ATP-dependent manner. A Brgl null mutation was produced and homozygotes die at implantation, but, because BrgI mRNA and protein are expressed at high levels in the oocyte, experiments have been designed to determine whether Brgl is required for zygotic genome activation. Interpretation of the peri-implantation phenotype has also been complicated by the fact that Brgl is the catalytic subunit of two distinct, but related, chromatin-remodeling complexes. Therefore, mice deficient for complex-specific subunits will be created to assess the relative importance of each complex. Finally, to move beyond implantation and elucidate Brgl function at later stages of embryonic and post-natal development, ENEJ mutagenesis and Cre-loxP conditional gene targeting is being used to examine its role in the development of the hematopoietic system.