C/EBP α and β mimic retinoic acid activation of IGFBP-5 in neuroblastoma cells by a mechanism independent from binding to their site
C/EBP α and β mimic retinoic acid activation of IGFBP-5 in neuroblastoma cells by a mechanism independent from binding to their site
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DOI：
10.1016/j.yexcr.2004.12.015
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发表时间：
2005-04-15
影响因子：
3.7
通讯作者：
Raschellà, G
中科院分区：
文献类型：
--
作者：
Cesi, V;Giuffrida, ML;Raschellà, G
胰岛素样生长因子介导的信号转导与神经母细胞瘤（NB）的侵袭行为有关，神经母细胞瘤是一种起源于神经嵴的儿童肿瘤。IGFBP-5是一种高亲和力结合IGFs的蛋白，在许多NB细胞系中表达，根据其浓度的不同，产生相反的作用。我们发现，在视黄酸（RA）介导的NB细胞分化过程中，IGFBP-5的表达增加。这是由于在基础和分化条件下进行的报告基因试验证明了转录激活。我们确定了人类IGFBP-5启动子中对RA敏感的最短区域（从核苷酸-83到+53）。该区域内CCAAT增强子结合蛋白（C/EBP）元件的突变增加了转录，表明该序列具有抑制作用。DNA亲和沉淀试验（DAPA）和染色质免疫沉淀表明，C/EBP α和C/EBP位点的结合在RA治疗后减少。C/EBP α并诱导人和小鼠NB细胞中IGFBP-5转录的增加，与RA处理后的结果相似。C/EBP α和β的激活并不依赖于它们与C/EBP位点的结合，因为它们仍然激活在C/EBP位点携带突变的IGFBP-5启动子。有趣的是，我们发现两种转录因子都能够与TATA盒子相互作用，但在ra诱导的分化过程中，只有C/EBPa相互作用增加。(c) 2005爱思唯尔公司版权所有。
Signal transduction mediated by insulin-like growth factors is implicated in the aggressive behavior of neuroblastoma (NB), a childhood tumor originating from the neural crest. IGFBP-5, a protein that binds IGFs with high affinity, is expressed in many NB cell lines exerting opposite effects, depending on its concentration. We found that IGFBP-5 expression increased during retinoic acid (RA)-mediated differentiation of NB cells. This was due to transcriptional activation as demonstrated by reporter assays carried out in basal and differentiating conditions. We defined the shortest region of the human IGFBP-5 promoter (from nucleotide -83 to +53) which is sensitive to RA. Mutation of a CCAAT enhancer binding protein (C/EBP) element inside this region increased transcription, suggesting a repressive role of this sequence. DNA Affinity Precipitation Assays (DAPA) and chromatin immunoprecipitation demonstrated that the binding of C/EBP alpha and to the C/EBP site decreased upon treatment with RA. C/EBP alpha and induced an increase in IGFBP-5 transcription in human and murine NB cells similar to that obtained upon RA treatment. Activation by C/EBP alpha and beta did not depend on their binding to the C/EBP site, since they still activated IGFBP-5 promoter carrying a mutation in the C/EBP site. Of interest, we found that both transcription factors were able to interact with the TATA box, but only C/EBPa interaction increased during RA-induced differentiation. (c) 2005 Elsevier Inc. All rights reserved.