Transcriptional regulation by epigenetic factors

描述(由申请人提供)：转录程序的表观遗传对细胞增殖、细胞分化和恶性转化是必不可少的。在分子上，转录程序的表观遗传在很大程度上依赖于通过扰乱细胞周期阶段保持染色质结构。尽管这种现象具有生物学上的重要性，但表观遗传的分子机制的细节仍然难以捉摸，主要是因为缺乏适当的实验方法。我们开发了新的实验范式，并发现许多染色体蛋白质在复制过程中与DNA相关。然而，甲基化的组蛋白在新生的DNA上以显著的延迟积累。我们的初步结果表明，在DNA复制之后，未分化的 细胞，包括小鼠胚胎干细胞(MESCs)，积累甲基化的组蛋白和恢复转录比相同来源的分化细胞慢。我们推测，这可能会在DNA复制时创建一个狭窄的时间窗口，具有唯一开放的染色质配置，缺乏组蛋白修饰和非常容易接收分化信号的转录。我们将通过检测在小鼠胚胎干细胞分化过程中DNA复制后不同修饰的组蛋白残基、组蛋白修饰和染色质重塑蛋白的积累来检验这一假设。我们还将检查这些细胞何时恢复转录，以及转录机制的组件何时被招募到新生DNA中。最后，我们将检验一个假设，即DNA复制后的短时间段，当染色质没有被修改时，为通过新诱导的转录因子的关联来获得分化信号提供了机会之窗。这可能解释了在获得新的转录程序时，未分化状态具有更高的可塑性。总体而言，这一提议将极大地促进细胞分化过程中的KE表观遗传学问题。

DESCRIPTION (provided by applicant): Epigenetic inheritance of transcriptional programs is essential for cell proliferation, cell differentiation and malignant transformation. Molecularly, epigenetic inheritance of transcriptional programs relies in large part on conservation of chromatin structure through disruptive cell cycle phases. Despite the biological importance of this phenomenon, the details of the molecular mechanisms of epigenetic inheritance are elusive, mostly because of the lack of appropriate experimental approaches. We developed new experimental paradigms, and found that many chromosomal proteins are associated with DNA during replication. However, methylated histones are accumulated on nascent DNA with significant delay. Our preliminary results suggest that following DNA replication, undifferentiated cells, including mouse embryonic stem cells (mESCs), accumulate methylated histones and resume transcription more slowly than differentiated cells of the same origin. We hypothesize that this may create a narrow time window at the time of DNA replication, with a uniquely open chromatin configuration lacking histone modifications and lacking transcription that is very susceptible to receiving signals for differentiation. We will test this hypothesis by examining th accumulation of different modified histone residues, histone-modifying and chromatin remodeling proteins following DNA replication during differentiation of mouse ESCs. We will also examine when transcription resumes in these cells, and when components of the transcriptional machinery are recruited to nascent DNA. Finally, we will test a hypothesis that the short period of time just after DNA replication, when chromatin is not modified, provides a window of opportunity for acquiring signals for differentiation through association of the newly induced transcription factors. This may account for a higher plasticity of undifferentiated states in acquiring new transcriptional programs. Overall, this proposal will greatly contribute to the ke epigenetic issues during cell differentiation.