Transcriptional control via CHR promoter elements: signaling proteins in cell cycle regulation

控制细胞分裂对预防癌症的发展很重要。一个中心机制代表转录的调节。我们和其他人已经描述了基于MuvB核心复合物的转录因子家族的功能。该家族控制着270多个基因，这些基因通常在细胞周期调控中发挥作用。DREAM、MMB、FOXM 1-MMB和FOXM 1-MuvB复合物通过结合到细胞周期基因同源区（Cell Cycle Genes Homology Region，CGE）启动子元件来调节转录。为了执行不同的功能，MuvB核心交换其关联伙伴。当MuvB结合E2 F/RB家族成员时，形成DREAM复合物。DREAM在G 0期和早期细胞周期中作为阻遏物发挥作用。一旦MuvB将其缔合伴侣转换为致癌转录因子B-MYB或FOXM 1以形成MMB、FOXM 1-MMB或FOXM 1-MuvB复合物，MuvB在细胞周期后期将其功能从阻遏物转变为转录激活物。这种MuvB/MUR系统的重要性已经很好地建立，但对信号蛋白触发四种MuvB复合物之间转换的机制的理解仍然有限。此外，在很大程度上还不清楚蛋白质是如何被募集来引起MuvB/muscle系统中的抑制或激活的。此外，MuvB复合物修饰染色质和连接到基础转录机器的机制仍然没有得到充分的理解。这个项目的目的是确定目前未知的蛋白质结合DNA间接通过双位点，并在确定其功能的信号通过双元件。总的目的是描绘的作用，新确定的因素控制细胞周期，通过MuvB/细胞周期系统。为此，我们将通过RIME/MS和APEX /MS方法鉴定与MuvB复合物相关的蛋白质。我们将测试这些因素是否需要间接DNA结合的双位点。将检查新鉴定的蛋白质与MuvB组分的相互作用。这些结果将阐明MuvB复合物上游信号传导的机制细节。我们将在敲除和敲除实验中研究新鉴定的因子的丢失如何有助于CHR调控的启动子的转录。此外，这些蛋白质对整体细胞周期调控的影响将在敲低/敲除后变得明显。在RNA-seq和ChIP-seq实验中，我们将确定这些蛋白质的靶基因及其通过转录对细胞周期调控的总体影响。总之，我们将确定未知的因素，作为转录因子，辅因子或信号蛋白作为下一个层次的调节MuvB/p53系统。我们将描述这些因素如何形成尚未知的联系，信号通路控制细胞分裂。除了提供对基本生物学过程的深入了解外，我们的研究结果还将对理解癌症的发展产生影响。

The control of cell division is important to prevent the development of cancer. A central mechanism represents the regulation of transcription. We and others have described the functions of a transcription factor family based on the MuvB core complex. This family controls more than 270 genes which typically play a role in cell cycle regulation. The DREAM, MMB, FOXM1-MMB and FOXM1-MuvB complexes regulate transcription through binding to the CHR (Cell Cycle Genes Homology Region) promoter element. To carry out different functions, the MuvB core exchanges its association partners. When MuvB binds members of the E2F/RB family, the DREAM complex is formed. DREAM functions as a repressor in G0 and the early cell cycle. MuvB changes its function from a repressor to a transcriptional activator during the later cell cycle once MuvB switches its association partners to the oncogenic transcription factors B-MYB or FOXM1 to form the MMB, FOXM1-MMB or FOXM1-MuvB complexes. The importance of this MuvB/CHR system is well established, but understanding of the mechanisms by which signaling proteins trigger the switch between the four MuvB complexes are still limited. Also, it is largely unknown how proteins are recruited to either cause repression or activation in the MuvB/CHR system. Furthermore, the mechanisms by which MuvB complexes modify chromatin and connect to the basal transcriptional machinery remain insufficiently understood. This proposed project aims at identifying currently unknown proteins binding DNA indirectly through CHR sites and at defining their function in signaling through CHR elements. The overall aim is to delineate the role of the newly identified factors in controlling the cell cycle through the MuvB/CHR system. To this end, we will identify proteins that are associated with the MuvB complex by the RIME/MS and APEX /MS methods. We will test whether these factors require the CHR site for indirect DNA binding. The interaction of the newly identified proteins with MuvB components will be examined. These results will elucidate the mechanistic details of signaling upstream of the MuvB complex. We will investigate in knockdown and knockout experiments how loss of the newly identified factors contributes to transcription of CHR-regulated promoters. Furthermore, the impact of these proteins on overall cell cycle regulation will become evident upon knockdown/knockout. In RNA-seq and ChIP-seq experiments we will define the target genes of these proteins and their overall impact on cell cycle regulation through transcription. Taken together, we will identify unknown factors that act as transcription factors, cofactors or signaling proteins as the next level of regulation in the MuvB/CHR system. We will delineate how these factors form yet unknown links to signaling pathways controlling cell division. Besides providing insight into fundamental biological processes, our results will also have implications for understanding the development of cancer.