Regulation of transcriptional coactivator p300 by posttranslational modification

点击翻译按钮获取中文摘要

The transcriptional coactivator p300 possess an intrinsic histone acetyltransferase (HAT) activity and is important for many cellular processes. A tight control of p300 is therefore critical to ensure locus-specific histone acetylation and gene regulation. We have established previously that p300 is dynamically regulated by posttranslational modification and distinct cellular distribution. We are the first to show that p300 is modulated by the cytoplasmic proteasome system. In addition, we have established that Akt/protein kinase B is a positive regulator of p300, while the B56γ3 regulatory subunit of protein phosphatase 2A (PP2A) is a negative regulator. Our works have provided novel insights into how cellular trafficking and spatial redistribution control the protein stability and transcriptional activity of p300. Recently, we found that p300 is regulated in a lineage specific manner during myogenic differentiation. As such, we intend to leverage our findings to define the molecular mechanisms underlying lineage-specific p300 regulation associated with myoblast differentiation. ******We hypothesize that reversible phosphorylaton plays critical roles in the control of p300 activity, which in turn modulates p300 function during myoblast differentiation, and propose to define the functional interactions of the B56γ3 regulatory subunit, Akt, and additional kinases with p300, in milieu of myoblast differentiation. We will survey p300 phosphorylation profiles and delineate the regulation of p300 by reversible phosphorylation with gain- and loss-of-function approaches. We will generate mutants that mimic candidate site phosphorylation and produce antibodies against site-specific phosphorylation to study the impact of reversible phosphorylation on p300 stability and transcriptional activity. Our goals are to determine the molecular basis for posttranslational modification-mediated p300 regulation and their consequences on the function of p300 as a HAT, a scaffold or a bridge on chromatin with respect to gene transcription. We will define the molecular mechanisms underlying different signaling pathways and p300 regulation pertinent to cellular differentiation. Our long term goals are to determine how these regulatory mechanisms control p300-dependent gene expression from intracellular trafficking, protein turnover to transcriptional activation, and to determine the molecular basis for p300 function in a network biology fashion. ******This research program is founded upon our recent findings and anchored on the p300 which is essential for different cellular processes and skeletal myogenesis in vivo. Many HQP will be trained through the proposed research as shown by our proven track record, and as a result, they will be well equipped to navigate into their own career path successfully and to contribute to our research field and different Canadian organizations significantly.