Pooley John R, Flynn Ben P, Grøntved Lars, Baek Songjoon, Guertin Michael J, Kershaw Yvonne M, Birnie Matthew T, Pellatt Annie, Rivers Caroline A, Schiltz R Louis, Hager Gordon L, Lightman Stafford L, Conway-Campbell Becky L
Henry Wellcome Laboratories for Integrated Neuroscience and Endocrinology, University of Bristol, Bristol BS1 3NY, United Kingdom.
Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense, Denmark.
Endocrinology. 2017 May 1;158(5):1486-1501. doi: 10.1210/en.2016-1929.
Glucocorticoids regulate hippocampal function in part by modulating gene expression through the glucocorticoid receptor (GR). GR binding is highly cell type specific, directed to accessible chromatin regions established during tissue differentiation. Distinct classes of GR binding sites are dependent on the activity of additional signal-activated transcription factors that prime chromatin toward context-specific organization. We hypothesized a stress context dependency for GR binding in hippocampus as a consequence of rapidly induced stress mediators priming chromatin accessibility. Using chromatin immunoprecipitation sequencing to interrogate GR binding, we found no effect of restraint stress context on GR binding, although analysis of sequences underlying GR binding sites revealed mechanistic detail for hippocampal GR function. We note enrichment of GR binding sites proximal to genes linked to structural and organizational roles, an absence of major tethering partners for GRs, and little or no evidence for binding at negative glucocorticoid response elements. A basic helix-loop-helix motif closely resembling a NeuroD1 or Olig2 binding site was found underlying a subset of GR binding sites and is proposed as a candidate lineage-determining transcription factor directing hippocampal chromatin access for GRs. Of our GR binding sites, 54% additionally contained half-sites for nuclear factor (NF)-1 that we propose as a collaborative or general transcription factor involved in hippocampal GR function. Our findings imply a dose-dependent and context-independent action of GRs in the hippocampus. Alterations in the expression or activity of NF-1/basic helix-loop-helix factors may play an as yet undetermined role in glucocorticoid-related disease susceptibility and outcome by altering GR access to hippocampal binding sites.
糖皮质激素部分通过糖皮质激素受体（GR）调节基因表达来调控海马体功能。GR结合具有高度细胞类型特异性，靶向组织分化过程中形成的可及染色质区域。不同类别的GR结合位点依赖于其他信号激活转录因子的活性，这些转录因子使染色质向特定背景下的组织形式转变。我们推测，由于快速诱导的应激介质引发染色质可及性，海马体中GR结合存在应激背景依赖性。通过染色质免疫沉淀测序来探究GR结合情况，我们发现束缚应激背景对GR结合没有影响，尽管对GR结合位点的序列分析揭示了海马体GR功能的机制细节。我们注意到与结构和组织作用相关基因附近的GR结合位点富集，GR缺乏主要的拴系伴侣，并且几乎没有证据表明其在负性糖皮质激素反应元件处结合。在一部分GR结合位点的下方发现了一个与NeuroD1或Olig2结合位点非常相似的基本螺旋-环-螺旋基序，我们提出它作为指导GR进入海马体染色质的候选谱系决定转录因子。在我们检测的GR结合位点中，54%还包含核因子（NF）-1的半位点，我们认为NF-1是参与海马体GR功能的协同或通用转录因子。我们的研究结果表明GR在海马体中具有剂量依赖性且与背景无关的作用。NF-1/基本螺旋-环-螺旋因子表达或活性的改变可能通过改变GR对海马体结合位点的可及性，在糖皮质激素相关疾病易感性和转归中发挥尚未确定的作用。
