Maintenance of unresponsiveness to self-antigens is essential for the prevention of autoimmunity but is anincompletely understood process. Our studies will focus on certain biochemical features of regulatory T cells(Treg) and how the Foxp3 complex mediates its repressive effects. While it is clear that mutations in humanFOXP3 predispose individuals to human autoimmune conditions, it is unclear why the mutant protein fails tofunction as a transcriptional regulator. There is also limited detail of how FOXP3 itself interacts with thetranscriptional machinery and which components of the FOXP3 ensembles exert phenotypic changes torender cells able to mediate suppression. Our proposed studies focus on the biochemistry of FOXP3complexes, as well as in vivo models to examine modification of Treg function through rational biochemicalalteration of the FOXP3 ensemble. The studies provide compelling evidence that a complex of specifichistone acetyl transferases and histone deacetylases (HDAC) associate with FOXP3 to create atranscriptional represser. FOXP3 becomes acetylated and phosphorylated and is then able to mediate itsactivities.The essential areas of the grant focus on the signaling effects that lead to post translational changes andfunctions of the FOXP3 ensemble. A dominant theme that emerges is that FOXP3 is acted on by enzymesthat modify its activity and stability and interactions with chromatin which lead to alterations in the actions ofTreg in vitro and in vivo. A rational therapeutic emerges from these studies employing HDAC inhibitors toincrease Treg acetylation modifications at specific lysine residues and thereby increase Treg function toameliorate autoimmunity.The goal of Project 1 is to provide basic biochemical information of how the FOXP3 complex binds tochromatin in human cells. This information will be helpful in Andrew Wells's study of mouse chromatin-FoxpS interactions and will be useful in the creation of transgenic and mutant mice that will help the Hancockproject and the Wells project. Human and mouse FOXP3 complexes appear to have differences.The intent of this project is to identify individual residues that are acetylated and phosphorylated andsubdomains that mediate interactions with other repressive components. This information will provide aframework for Andrew Wells to examine chromatin remodeling events in the mouse and for Wayne Hancockto examine functional relevance in in vivo models.
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