Mechanisms of condensin-mediated gene regulation in C. elegans

项目概要/摘要 染色体结构的调节是基因组功能的基础。在真核生物中，一个关键的调节因子 染色体结构是一种进化上保守的蛋白质复合物，称为凝缩蛋白，它对于 细胞分裂过程中染色体的浓缩和分离，在细胞分裂过程中的基因调控中发挥关键作用 间期。凝缩蛋白如何结合和调节染色体结构背后的分子机制 这如何影响转录仍不清楚。为了解决这个问题，我们使用了一种专门的凝缩素，其功能 线虫 X 染色体剂量补偿复合体 (DCC) 内。 DCC 特异性结合 和 将雌雄同体中两条 X 染色体的转录抑制为两倍。的共同选择 X染色体剂量补偿的凝缩蛋白提供了一个强大的实验模型来研究 控制凝缩蛋白结合特异性并分析凝缩蛋白介导的变化的机制 染色体结构和转录具有高精度，全部不受潜在的间接影响 染色体分离。 我们之前的工作表明，DCC 与 X 染色体的特异性和稳健结合是通过 逐步招募机制，然后线性扩散。首先，DCC以较小的位置进入染色体 由两个基因组特征定义的 X 特异性位点的数量：存在多个 12 bp 募集基序 并与高占用转录因子靶位点重叠。 X特定条目后，附加站点 长距离合作以提高染色体上 DCC 招募的水平。从 DCC沿着大的染色体结构域线性扩散，在活性基因处积累 X. DCC 结合的调控元件导致染色体范围的转录抑制、变化 在特定组蛋白修饰、染色体压缩和长程染色体水平上 互动。在这里，我们将解决有关 DCC 招募、传播和传播的几个重要问题。 使用一组强大的遗传、基因组和成像方法发挥功能：1) DCC 如何识别 X 上初始入口站点的功能？ 2）远距离合作背后的机制是什么 DCC 招聘要素之间？ 3) DCC如何传播以及DCC介导的染色体相互作用 监管？ 4）DCC抑制转录的机制是什么？ 我们的工作成果将阐明凝缩蛋白发挥作用的基本分子机制 真核生物中广泛的基本功能。这与人类健康相关，因为凝缩蛋白结构 从秀丽隐杆线虫到人类，其功能都高度保守，确定凝缩蛋白的功能是关键 了解染色体结构对健康和疾病中基因组功能的贡献。

PROJECT SUMMARY/ABSTRACT Regulation of chromosome structure is fundamental for genome function. Across eukaryotes, a key regulator of chromosome structure is an evolutionarily conserved protein complex called condensin, which is essential for chromosome condensation and segregation during cell division and play key roles in gene regulation during interphase. The molecular mechanisms behind how condensins bind and regulate chromosome structure and how this affects transcription remain unclear. To address this, we use a specialized condensin that functions within the X chromosome dosage compensation complex (DCC) in C. elegans. DCC specifically binds to and represses transcription of both X chromosomes in hermaphrodites by a factor of two. The co-option of condensin for X chromosome dosage compensation provides a powerful experimental model to study the mechanisms that control specificity of condensin binding and to analyze condensin-mediated changes in chromosome structure and transcription with high precision, all free from potential indirect effects on chromosome segregation. Our previous work suggests that specific and robust DCC binding to the X chromosomes is accomplished by a step-wise recruitment mechanism followed by linear spreading. First, DCC enters the chromosome at a small number of X-specific sites defined by two genomic features: the presence of multiple 12-bp recruitment motifs and overlap with high occupancy transcription factor target sites. After X-specific entry, additional sites cooperate over long-distance to increase the level of DCC recruitment across the chromosome. From the recruitment sites, DCC spreads linearly along large chromosomal domains, accumulating at active gene regulatory elements across the X. DCC binding leads to chromosome-wide transcriptional repression, changes in the level of specific histone modifications, chromosome compaction, and long-range chromosomal interactions. Here, we will address several important questions regarding DCC recruitment, spreading and function using a powerful set of genetic, genomic and imaging approaches: 1) How does the DCC recognize features of the initial entry sites on the X? 2) What is the mechanism behind long-distance cooperation between DCC recruitment elements? 3) How is DCC spreading and DCC-mediated chromosomal interactions regulated? 4) What is the mechanism by which the DCC represses transcription? The outcome of our work will elucidate the basic molecular mechanisms by which condensins perform their wide-range of essential functions in eukaryotes. This is relevant to human health because condensin structure and function is deeply conserved from C. elegans to humans, and determining how condensins function is key to understanding the contribution of chromosome structure to genome function in health and disease.