A Function of β-Arrestin 1 in Nucleus: Epigeneticly Regulates Gene Transcription and its Role in Autoimmunity u[
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Shi Yufeng N/K. %<h
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Chromatin modification is considered to be a fundamental mechanism of regulating gene expression to generate coordinated responses to environmental changes. β-arrestin 1 (βarr1) is a multifunctional molecule active in many signaling pathways. In the first part of this thesis, we show that nuclear βarr1 accumulation caused by certain GPCR stimulation or βarr1 overexpression, induces its binding at specific gene promoters where it facilitates the recruitment of histone acetyltransferase p300，resulting in enhanced local histone H4 acetylation and transcription of these genes. These results reveal a novel function of βarr1 on epigenetic regulation, and elucidate a direct way for GPCR signaling from cell membrane to the nucleus. Further, in the second part of this thesis, we foud a function of βarr1 in CD4+ T cells. As demostrated by in vitro and in vivo experiments, nuclear βarr1 epigeneticly regulates Bcl-2 expression and the survival of CD4+ T cells. Importantly, βarr1 knock out mice were found to be significantly more resistant to experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), while βarr1 over-expression in transgenic mice increased susceptibility to the disease. Moreover, we found that the expression of βarr1 is significantly increased in CD4+ T cells isolated from multiple sclerosis patients and EAE mice, and this βarr1 upregulation renders the auto-reactive CD4+ T cells more resistant to cytokine-withdrawal-induced apoptosis. Thus, these results not only reveal an improtant biological significance of the nuclear function of βarr1, epigeneticly regulating gene expression, and also demostrate a novel regulatory mechanism critical for CD4+ T cell survival and autoimmunity, and suggest a potential new therapeutic strategy for autoimmune disease. l|k`YC x
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Key borad: β-arrestin 1, G protein coupled receptor, epigenetic modification, autoimmunity.
