Gene Regulation Mechanisms by the APP/Fe65/TIP60 Complex

描述（由申请人提供）：我们的长期目标是阐明淀粉样前体蛋白（APP）信号响应中人类基因表达转录调控的分子机制。APP是一种跨膜蛋白，是β -淀粉样肽（Abeta）的前体，是阿尔茨海默病淀粉样斑块的主要成分。这种肽是由APP通过分泌酶和分泌酶的蛋白水解而产生的。

DESCRIPTION (provided by applicant): Our long-term objective is to elucidate the molecular mechanisms of transcriptional regulation of human gene expression in response to Amyloid Precursor Protein (APP) signaling. APP is a transmembrane protein that is the precursor of the beta-amyloid peptide (Abeta), the major component of amyloid plaques that characterize Alzheimer's disease. This peptide is generated from APP through proteolysis by the beta- and gamma-secretases. Following proteolysis, the released 47-residue cytoplasmic domain of APP (APP-C) interacts with the proteins Fe65 and TIP60, forming a nuclear complex that regulates gene expression. However, despite the central importance of the APP-C in human physiology and Alzheimer's disease pathogenesis, the sequence-specific DNA-binding transcription factors that recruit the TIP60/Fe65/APP-C complex onto the promoters of human genes and the molecular mechanisms underlying the transcriptional regulation by this complex remain elusive. TIP60 has histone acetyltransferase (HAT) activity with unique substrate specificity and interacts with class I nuclear receptors, supporting the hypothesis that these transcription factors may mediate APP-C signaling in the nucleus. This proposal will test this hypothesis and will focus on a mechanistic analysis of the APP-C signaling in gene regulation. The Specific Aims are: 1) To dissect the molecular mechanisms of gene regulation by the TIP60/Fe65/APP-C complex through its association with the androgen and estrogen receptors, using protein-protein interaction assays, in combination with site-directed mutagenesis and transient transfection experiments. 2) To elucidate the structural basis of the TIP60 HAT substrate specificity and the structural determinants of the TIP60 interaction with the androgen and estrogen receptors. 3) To determine the three-dimensional conformational changes induced on the TIP60/Fe65 complex by the APP-C binding, using X-ray crystallography. These studies will provide high-resolution three-dimensional structures of the TIP60, Fe65, and APP-C proteins, and will provide mechanistic insights into the regulation of human gene expression in response to APP signaling. This information could be used for the development of novel strategies in the treatment of Alzheimer's disease.