Transcriptional regulation by epigenetic factors

描述（由申请人提供）：转录程序的表观遗传对于细胞增殖、细胞分化和恶性转化至关重要。在分子水平上，转录程序的表观遗传在很大程度上依赖于通过破坏性的细胞周期阶段保持染色质结构。尽管这种现象的生物学意义，表观遗传遗传的分子机制的细节是难以捉摸的，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，发现许多染色体蛋白质在复制过程中与DNA相关。然而，甲基化组蛋白在新生DNA上的积累具有显著的延迟。我们的初步结果表明，在DNA复制后， 细胞（包括小鼠胚胎干细胞（mESC））积累甲基化组蛋白，并且比相同来源的分化细胞更慢地恢复转录。我们假设，这可能会在DNA复制时产生一个狭窄的时间窗口，具有独特的开放染色质构型，缺乏组蛋白修饰，缺乏非常容易接收分化信号的转录。 我们将通过检测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验证这一假设。我们还将研究转录何时在这些细胞中恢复，以及转录机制的组成部分何时被招募到新生DNA中。最后，我们将测试一个假设，即DNA复制后的短时间内，当染色质没有被修改，提供了一个窗口的机会，通过新诱导的转录因子的协会获得分化的信号。这可能是未分化状态在获得新的转录程序时具有更高可塑性的原因。总的来说，这一建议将大大有助于细胞分化过程中的ke表观遗传问题。

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.