Division of Endocrinology and Metabolism, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
Metabolism. 2012 Nov;61(11):1622-32. doi: 10.1016/j.metabol.2012.04.014. Epub 2012 May 16.
Adiponectin is a hormone that modulates many metabolic processes and is exclusively expressed in adipose tissue. However, complete understanding of the factors that regulate adiponectin expression is lacking. The following were investigated: (1) functional analysis of the human adiponectin promoter, (2) putative adiponectin repressor sequence activity in 3T3-L1 adipocytes using promoter mutagenesis, (3) whether Snail, an E-box binding transcription factor, binds this repressor sequence, (4) if Snail regulates adiponectin expression in 3T3-L1 pre-adipocytes.
MATERIALS/METHODS: To further understand how adiponectin expression is regulated, we isolated the human adiponectin promoter and analyzed its activity after serial deletions.
We found a negative cis-regulatory element located in the adiponectin proximal promoter sequence (-174 to -152 bp), which contained an E-box site (CAACTG). The DNA binding activity of this putative negative regulatory factor was found to be sequence-specific and the binding activity is decreased during adipocyte differentiation time-dependently. Affinity chromatography identified the zinc-finger transcription factor Snail (SNAI1) as the putative negative regulatory factor. Chromatin immunoprecipitation assay and electrophoretic mobility shift assay confirmed that Snail binds to this negative cis-regulatory element in pre-adipocytes, exclusively. Inhibition of Snail expression using small interfering RNA techniques increased adiponectin expression in 3T3-L1 adipocytes, while overexpression of Snail reduced adiponectin expression. Furthermore, we observed an inverse relation between the expression of Snail and the expression of CCAAT-enhancer-binding protein alpha and peroxisome proliferator-activated receptor gamma, which are transcription factors that regulate adipogenesis.
Snail is a novel regulator of adiponectin expression and probably has a role in regulating adipogenesis.
脂联素是一种调节多种代谢过程的激素，仅在脂肪组织中表达。然而，调控脂联素表达的因素尚不完全清楚。本研究旨在：（1）对人脂联素启动子进行功能分析；（2）通过启动子突变，研究 3T3-L1 脂肪细胞中假定的脂联素阻遏序列的活性；（3）E-盒结合转录因子 Snail 是否结合该阻遏序列；（4）Snail 是否调节 3T3-L1 前脂肪细胞中的脂联素表达。
材料/方法：为了进一步了解脂联素表达是如何调控的，我们分离了人脂联素启动子并分析了其在连续缺失后的活性。
我们发现位于脂联素近端启动子序列（-174 至-152bp）中的一个负性顺式调控元件，其中包含一个 E-盒位点（CAACTG）。该假定的负性调节因子的 DNA 结合活性具有序列特异性，并且在脂肪细胞分化过程中，结合活性随时间呈下降趋势。亲和层析鉴定锌指转录因子 Snail（SNAI1）为潜在的负性调节因子。染色质免疫沉淀和电泳迁移率变动分析证实，Snail 在原代脂肪细胞中特异性结合该负性顺式调控元件。使用小干扰 RNA 技术抑制 Snail 表达可增加 3T3-L1 脂肪细胞中的脂联素表达，而过表达 Snail 则降低脂联素表达。此外，我们观察到 Snail 的表达与 CCAAT 增强子结合蛋白-α和过氧化物酶体增殖物激活受体-γ的表达呈负相关，后者是调节脂肪生成的转录因子。
Snail 是脂联素表达的一种新型调节因子，可能在调节脂肪生成中发挥作用。
