Characterization of the p53-CBP/p300 Transcriptional Activator-Coactivator Complex

项目摘要 CREB结合蛋白（CBP）及其辅因子p300是主要的转录辅激活因子， 整合了许多信号通路，在细胞增殖、分化 细胞凋亡和DNA修复。CBP和p300的生物学功能主要通过 多个转录因子相互作用结构域以及组蛋白乙酰转移酶（HAT） 域然而，转录因子如何与CBP和p300复合的结构模型， 缺乏调节辅激活因子功能。CBP和p300的一个被充分研究的细胞伴侣是 肿瘤抑制蛋白p53。一些研究表明，DNA损伤时，CBP/p300是 由p53募集以修饰染色质并帮助p53靶基因的转录激活。它 已经假设活性p53的四个转录激活结构域中的每一个 四聚体与单个CBP/p300分子的四个独立结构域结合， 进一步稳定p53-CBP/p300复合物并增强p53介导的 转录。然而，p53结合对局部和整体构象变化的影响， 在CBP/p300中，其对组蛋白乙酰转移酶活性的影响尚未确定。使用 单粒子电子显微镜、溶液生物物理和生物化学方法的组合， 拟议工作的目标是开发一个全面的结构-功能模型， CBP/p300在p53介导的转录激活中的作用

PROJECT SUMMARY The CREB-binding protein (CBP) and its paralog p300 are master transcriptional coactivators that integrate numerous signaling pathways and play critical roles in cell proliferation, differentiation, apoptosis, and DNA repair. The biological functions of CBP and p300 are largely exerted through multiple transcription factor interaction domains as well as a histone acetyl transferase (HAT) domain. However, a structural model of how transcription factor complexes with CBP and p300 modulate coactivator function is lacking. A well-studied cellular partner of CBP and p300 is the tumor suppressor protein p53. Several studies suggest that upon DNA damage CBP/p300 is recruited by p53 to modify chromatin and aid in transcriptional activation of p53 target genes. It has been hypothesized that each of the four transcriptional activation domains of an active p53 tetramer bind to four separate domains of a single CBP/p300 molecule, resulting in increased avidity that further stabilizes the p53-CBP/p300 complex and enhances p53-mediated transcription. However, the influence of p53 binding on local and global conformational changes in CBP/p300 and its effect on histone acetyltransferase activity has yet to be defined. Using a combination of single particle electron microscopy, solution biophysical and biochemical methods, the goal of the proposed work is to develop a comprehensive structure-function model of CBP/p300 in p53-mediated transcriptional activation.