Connecting Myc to transcriptional regulation through cyclin-dependent kinases

MYC蛋白是一种转录因子，通过激活和抑制转录来显著改变基因的表达。人类有三个Myc蛋白家族成员(c-Myc、N-Myc、L-Myc)。这些都是人类癌症中最常见的失调蛋白，在分子水平上了解它们的功能对于开发新的治疗方法至关重要。在小鼠癌症模型上的优雅研究证实了Myc的抑制是一种治疗策略，但开发直接针对Myc蛋白的临床化合物的努力失败了。这是因为Myc蛋白具有内在的无序结构，因此缺乏稳定的表面特征来靶向小分子。相反，我们认为Myc最好的靶向是阻断Myc和其他驱动致癌基因表达的因素之间的蛋白质-蛋白质相互作用。本项目旨在从分子和细胞水平表征Myc和P-TEFb之间的相互作用。P-TEFb是CDK9和Cyclin T1的复合体，通过释放RNA聚合酶II的延长暂停状态来驱动转录激活。CDK9的抑制剂正在研究中，作为Myc驱动的癌症的潜在治疗药物。然而，由于我们对CDK9转录功能的分子机制缺乏了解，以及开发高选择性CDK9抑制剂的挑战，这些抑制剂的临床开发受到了阻碍。该项目将研究Myc结合对P-TEFb催化活性的影响以及CDK9抑制剂的抑制作用，并阐明Myc与P-TEFb之间的复合体的结构。还将建立基于细胞的分析来确定相互作用的定位和细胞周期调节，利用这一点来验证他们的生化和结构研究，并探索调节相互作用的因素。最后，将使用Omics方法评估干扰Myc/P-TEFb相互作用对转录的影响。

Myc proteins are transcription factors that markedly alter gene expression through both activation and repression of transcription. There are three Myc protein family members in humans (c-Myc, N-Myc, L-Myc). These are among the most frequently dysregulated proteins in human cancer, and understanding their functions at a molecular level is critical for the development of new treatments. Elegant studies in mouse models of cancer have validated the inhibition of Myc as a therapeutic strategy, but efforts to develop clinical compounds that target Myc proteins directly have failed. This is because Myc proteins have intrinsically disordered structures and are therefore lacking in stable surface features to target with small molecules. Instead, we believe that Myc is best targeted through blocking the protein-protein interactions between Myc and other factors that drive oncogenic gene expression. This project aims to characterize the interaction between Myc and P-TEFb at a molecular and cellular level. P-TEFb is a complex of CDK9 with Cyclin T1 that drives transcriptional activation through release of the elongation pause state of RNA polymerase II. Inhibitors of CDK9 are under investigation as potential cancer therapeutics in Myc-driven cancers. However, clinical development of these inhibitors is hampered by our lack of understanding of the molecular mechanisms of CDK9 function in transcription, and the challenge of developing highly selective CDK9 inhibitors. The project will investigate the effect of Myc binding on P-TEFb catalytic activity and inhibition by CDK9 inhibitors, and elucidate the structure of the complex between Myc and P-TEFb. Cell-based assay will also be established to determine the localisation and cell-cycle regulation of the interaction, use this to validate their biochemical and structural studies, and explore factors that regulate the interaction. Finally, the consequences of disrupting the Myc/P-TEFb interaction on transcription will be assessed using Omics approaches.