Dissecting the mechanistic role of multinucleation in breast and trophoblast cancers

项目总结/摘要 癌症的一个关键驱动因素是细胞中转录网络的全球失调。转录输出 依赖于染色质结构和拓扑结构;被抑制的基因与活性基因隔离， 核膜附近的致密DNA区域。密集的染色体区域，称为异染色质， 与异染色质蛋白-1（HP 1）相关，并通过与 核跨膜蛋白核纤层蛋白结合受体（LBR）和中间丝蛋白核纤层蛋白 B。因此，经历转录的整体重新布线的癌细胞也经常表现出异常蛋白质， 核纤层蛋白B、LBR和HP 1的表达。这些蛋白质失调的物理表现是 核被膜的大小和形状的变形。事实上，这种核多形性被用作 肿瘤进展的组织学标志物。在雌激素受体阳性（ER+）乳腺癌患者中， HP 1的下调以及核纤层蛋白B和LBR的上调与早期发生的 远端转移了解控制异染色质在染色体上组装的生物物理特性， 核外围将促进旨在恢复适当基因调节的疗法的开发。HP 1是 最近发现在体外将DNA和染色质浓缩成液-液相分离（LLPS）液滴。这 表明了体内DNA组织的潜在机制。为了研究HP 1的分子细节， 介导的压实和相分离，我利用DNA窗帘和共聚焦显微镜。我找到了钥匙 多价-LLPS相互作用和DNA压缩所需的HP 1区域。本项前期研究 重点是DNA，目标1的研究生工作将建立在这些研究的基础上，评估HP 1与 复杂的核小体底物。异染色质在体内的区别在于均匀分布的核小体， 组蛋白H3赖氨酸9（H3 K9 me 3）的三甲基化。我将制作染色质底物，范围从单- 核小体到50 kb染色质纤维的间距和甲基化修饰的变化。我会监察 结合，寡聚化和相分离的HP 1在这些基板上的组合，散装生化 分析和新的单分子染色质分析。目标2中拟议的博士后研究将侧重于 确定核外围的物理模型。我将重组染色质之间的相互作用 以及体外单分子研究和细胞超分辨研究的薄层。我会用细胞系 乳腺癌转移的小鼠模型，以确定指导转移复发的分子机制 Lamin B和LBR高表达的ER+乳腺癌患者。这个研究项目将推动我 我的最终目标是领导我自己的实验室研究细胞核拓扑结构如何与细胞命运决定相结合 以及导致疾病的失调。

Project Summary/Abstract A key driver of cancer is the global deregulation of transcription networks in the cell. Transcriptional output is dependent on chromatin structure and topology; repressed genes are sequestered from active genes into regions of compacted DNA near the nuclear membrane. Dense chromosomal domains, termed heterochromatin, are associated with Heterochromatin Protein-1 (HP1) and are tethered to the periphery via an interaction with the nuclear transmembrane protein, Lamin Binding Receptor (LBR), and the intermediate filament protein, Lamin B. Consequently, cancer cells that undergo global rewiring of transcription also often exhibit aberrant protein expression of Lamin B, LBR and HP1. The physical manifestation of the misregulation of these proteins is distortion in the size and shape of the nuclear envelope. Indeed, this nuclear pleomorphism is used as a histological marker of tumor progression. In estrogen receptor positive (ER+) breast cancer patients, downregulation of HP1 and upregulation of Lamin B and LBR is strongly correlated with earlier occurrence of distal metastasis. Understanding the biophysical properties that govern the assembly of heterochromatin at the nuclear periphery will facilitate the development of therapies aimed at restoring proper gene regulation. HP1 was recently found to concentrate DNA and chromatin into liquid-liquid phase separated (LLPS) droplets in vitro. This suggests a potential mechanism of DNA organization in vivo. To investigate the molecular details of HP1- mediated compaction and phase separation, I utilized DNA curtains and confocal microscopy. I identified key regions of HP1 required for multivalent—LLPS interactions and DNA compaction. This preliminary research focused on DNA, and the graduate work in Aim 1 will build on these studies by evaluating HP1 interactions with complex nucleosomal substrates. Heterochromatin in vivo is distinguished by evenly spaced nucleosomes and the trimethylation of histone H3 lysine 9 (H3K9me3). I will make chromatin substrates that range from mono- nucleosomes to 50kb chromatin fibers with variations in spacing and methylation modification. I will monitor the binding, oligomerization and phase separation of HP1 on these substrates by a combination of bulk biochemical assays and a novel single molecule chromatin assay. The proposed postdoctoral research in Aim 2 will focus on determining a physical model of the nuclear periphery. I will reconstitute the interactions between chromatin and the lamina with single molecule studies in vitro and super resolution studies in cells. I will use cell lines and mouse models of breast cancer metastasis to determine the molecular mechanism guiding metastatic recurrence of ER+ breast cancer patients with high expression of Lamin B and LBR. This research program will propel me toward my ultimate goal of leading my own lab studying how nuclear topology is coupled to cell fate determination in development, and the misregulation that leads to disease.