Chromatin Landscaping of TGF-P/SMAD Signaling Targets

TGF-β/SMAD信号网络在正常上皮细胞的生长抑制中起重要作用。在肿瘤过程中，TGF-β/SMAD信号传导的遗传和表观遗传损失可导致转化细胞的生长和侵袭。在卵巢癌中，最近有报道称，TGF-β/SMAD信号传导可以变得对TGF-β的激活剂无反应，尽管上游调节因子如TbetaRII在遗传上保持完整和功能。因此，似乎其他异常事件，可能影响辅激活因子， 或该生长抑制途径的共阻遏物，触发TGF-β/SMAD下游靶标的表观遗传扰动。这些尚未探索的扰动有可能逐渐改变靶基因启动子及其周围的染色质结构，并且可能是体细胞遗传的。我们推测，表观遗传失调TGF-β/SMAD信号可能会改变TGF-β/SMAD靶基因的转录谱，导致卵巢表面上皮肿瘤生长的启动和促进。为了验证我们的假设，我们将全面调查和比较区域染色质概况（活性或抑制状态）的TGF-β/SMAD在卵巢癌和正常上皮细胞的目标启动子。相对于这种表观遗传现象，SMAD介导的转录调控还依赖于其他机制，如组织特异性因子、启动子序列以及与其他DMA结合转录因子的协同相互作用。我们将使用计算工具来确定假定的TGF-β/SMAD靶序列，并确定它们与卵巢上皮局部染色质结构的功能关系。将开发一种新的基于微阵列的ChIP-芯片测定以实验性地确定染色质重塑（即，组蛋白修饰）在卵巢癌中发生。统计方法将 提出模拟SMAD复合物和改变的染色质结构之间的相互作用，并在卵巢癌细胞中定义独特的表观遗传特征。具体而言，我们将1）开发KbTSMAD（TGF-β/SMAD信号通路知识库），TGF-β/SMAD信号通路及其直接靶基因启动子的信息资源; 2）确定卵巢癌细胞中这些下游基因座中染色质重塑的概况;和3）开发用于建模TGF-β/TGF-β 1之间的协同相互作用的统计方法。SMAD复合物和改变的染色质结构，并用于定义独特的表观遗传 卵巢癌细胞的特征。

The TGF-beta/SMAD signaling network plays an important role in growth inhibition of normal epithelia. In neoplastic processes, genetic and epigenetic losses of TGF-beta/SMAD signaling can result in outgrowth and invasion of transformed cells. In ovarian cancer, it has recently been reported that TGF-beta/SMAD signaling can become non-responsive to activators of TGF-beta, despite the fact that upstream regulators, such as TbetaRII, remain genetically intact and functional. Thus, it appears that other aberrant events, perhaps affecting co-activators or co-repressors of this growth inhibitory pathway, trigger epigenetic perturbations in TGF-beta/SMAD downstream targets. These as of yet un-explored perturbations have the potential to gradually alter chromatin structure in and around promoters of target genes and may be somatically heritable. We hypothesize that epigenetic deregulation TGF-beta/SMAD signaling may alter transcriptional profiles of TGF-beta/SMAD target genes, resulting in the initiation and promotion of neoplastic outgrowth of the ovarian surface epithelium. To test our hypothesis, we will comprehensively survey and compare regional chromatin profiles (active or repressed state) of TGF-beta/SMAD target promoters in ovarian cancer versus normal epithelia. Relative to this epigenetic phenomenon, SMAD-mediated transcription regulation also depends on other mechanisms, such as tissue-specific factors, promoter sequences, and cooperative interaction with other DMA-binding transcription factors. We will use computational tools to identify putative TGF-beta/SMAD target sequences and determine their functional relationship with local chromatin structure in ovarian epithelia. A novel microarray-based ChlP-on-chip assay will be developed to experimentally determine whether chromatin remodeling (i.e., histone modifications) of these predicted promoters occurs in ovarian cancer. Statistical approaches will be proposed to model the interaction between SMAD complexes and altered chromatin structure and to define unique epigenetic signatures in ovarian cancer cells. Specifically, we will 1) develop KbTSMAD (Knowledge base of TGF-beta/SMAD signaling pathway), an information resource of the TGF-beta/SMAD signaling pathway and its direct target gene promoters; 2) determine profiles of chromatin remodeling in these downstream loci in ovarian cancer cells; and 3) develop statistical approaches for modeling the synergistic interaction between TGF-beta/SMAD complex and altered chromatin structure and for defining unique epigenetic signatures in ovarian cancer cells.