Effects of acetylation on the function of a transcriptional co-activator

转录辅激活因子p300含有内在的组蛋白乙酰转移酶（HAT）活性，是一系列细胞过程所必需的。对p300的严格控制对于确保精确的组蛋白乙酰化和基因活化至关重要。我们已经确定，p300是动态调节的翻译后修饰和细胞分布。此外，我们是第一个表明，p300是由细胞质蛋白酶体系统调节。我们的研究提供了新的见解，细胞运输和空间再分布如何控制蛋白质的稳定性和转录活性的p300。有趣的是，p300是一个真正的乙酰化底物在体内，我们已经映射的乙酰化位点的C-末端区域。我们还发现，E1 A病毒蛋白，p300的阻遏物，增强p300自动乙酰化，同时抑制p300 HAT活性。基于这些观察，我们假设可逆乙酰化在控制p300活性中起着关键作用，这反过来又影响p300在重要细胞过程中的功能。我们将首先研究乙酰化对p300功能和周转的影响。我们将鉴定和表征p300中的特定乙酰化位点。我们还将产生模拟乙酰化位点的突变体，并产生针对特定乙酰化赖氨酸的抗体，以研究乙酰化对蛋白质稳定性和p300转录活性的影响。我们的目标是确定乙酰化介导的p300调节的分子基础及其对p300作为HAT、支架或染色质上的桥在转录激活方面的功能的影响。我们的长期目标是确定这些调控机制如何影响p300依赖的基因表达，从细胞内运输，蛋白质周转转录激活，并确定在网络生物学方式的p300调控的分子基础。

The transcriptional co-activator p300 contains an intrinsic histone acetyltransferase (HAT) activity and is required for an array of cellular processes. Tight control of p300 is critical to ensure precise histone acetylation and gene activation. We have established that p300 is dynamically regulated by post-translational modifications and cellular distributions. In addition, we are the first to show that p300 is regulated by the cytoplasmic proteasome system. Our studies have provided novel insight on how cellular trafficking and spatial redistributions control the protein stability and transcriptional activity of p300. Interestingly, p300 is a bona fide acetylation substrate in vivo, and we have mapped the acetylation sites to its C-terminal region. We also found that E1A viral protein, a repressor of p300, enhances p300 autoacetylation while repressing p300 HAT activity. Based on these observations, we hypothesize that reversible acetylation plays critical roles in the control of p300 activity, which in turn affects p300 function in important cellular processes. We will first study the effects of acetylation on p300 function and turnover. We will identify and characterize the specific acetylation sites in p300. We will also generate mutants that mimic the acetylation sites and produce antibodies against the specific acetylated-lysine to study the impact of acetylation on protein stability and transcriptional activity of p300. Our goal is to determine the molecular basis for acetylation-mediated p300 regulation and their consequences on the function of p300 as a HAT, a scaffold, or a bridge on chromatin with respect to transcriptional activation. Our long term goals are to determine how these regulatory mechanisms affect p300-dependent gene expression from intracellular trafficking, protein turnover to transcriptional activation, and to determine the molecular basis for p300 regulation in a network biology fashion.