Connecting Myc to transcriptional regulation through cyclin-dependent kinases

Myc蛋白是通过激活和抑制转录来显著改变基因表达的转录因子。在人类中存在三种Myc蛋白家族成员（c-Myc、N-Myc、L-Myc）。这些是人类癌症中最常见的失调蛋白质之一，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。在小鼠癌症模型中的优雅研究已经验证了Myc的抑制作为一种治疗策略，但开发直接靶向Myc蛋白的临床化合物的努力已经失败。这是因为Myc蛋白具有固有的无序结构，因此缺乏稳定的表面特征以用小分子靶向。相反，我们认为Myc最好通过阻断Myc与其他驱动致癌基因表达的因子之间的蛋白质-蛋白质相互作用来靶向。该项目旨在在分子和细胞水平上表征Myc和P-TEFb之间的相互作用。P-TEFb是CDK 9与细胞周期蛋白T1的复合物，其通过释放RNA聚合酶II的延长暂停状态来驱动转录激活。CDK 9抑制剂作为Myc驱动的癌症的潜在癌症治疗剂正在研究中。然而，由于我们对CDK 9在转录中功能的分子机制缺乏了解，以及开发高选择性CDK 9抑制剂的挑战，这些抑制剂的临床开发受到阻碍。该项目将研究Myc结合对P-TEFb催化活性的影响以及CDK 9抑制剂的抑制作用，并阐明Myc和P-TEFb之间复合物的结构。还将建立基于细胞的测定法，以确定相互作用的定位和细胞周期调节，利用这一点来验证其生化和结构研究，并探索调节相互作用的因素。最后，将使用组学方法评估破坏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.