Department of Molecular Biology and Genetics, Istanbul Technical University, Istanbul, Turkey.
J Neurochem. 2011 May;117(4):724-34. doi: 10.1111/j.1471-4159.2011.07243.x. Epub 2011 Apr 6.
The most common cause of autosomal dominant hereditary spastic paraplegia, that is characterized with axonal degeneration in corticospinal tracts and posterior columns, is known to be caused by mutations in the SPG4 gene which encodes spastin, a microtubule severing ATPase belonging to AAA family. Spastin promotes the formation of microtubule networks that are essential for axon growth and branching which are important for neuronal plasticity. Mutations observed in SPG4 gene of hereditary spastic paraplegia patients have been shown to cause reduced spastin levels. In addition to mutations, transcriptional regulation of spastin gene expression may also affect spastin level. ETS (E Twenty Six-specific)-domain transcription factor, Elk1, has been shown to be important for synaptic plasticity and interact with microtubules. In this study, we aimed to identify the critical promoter regions of SPG4 gene and effects of Elk on SPG4 gene expression. We identified 700 bp TATA-less promoter including a critical CpG island as an optimal promoter, and deletion of the CpG island gradually decreased the SPG4 promoter activity. In addition, we identified the binding sites of Elk1 on the SPG4 promoter by EMSA. Over-expression of Elk1 showed that it repressed the SPG4 promoter and also decreased spastin protein level in SHSY-5Y cells.
常染色体显性遗传性痉挛性截瘫最常见的病因是 SPG4 基因突变，该基因编码微管切割 ATP 酶，属于 AAA 家族的 spastin。SPG4 基因突变导致 axonal 退行性变，在皮质脊髓束和后柱中更为明显。spastin 促进微管网络的形成，微管网络对于轴突生长和分支至关重要，而轴突生长和分支对于神经元可塑性也很重要。遗传性痉挛性截瘫患者 SPG4 基因突变导致 spastin 水平降低。除了突变，spastin 基因表达的转录调控也可能影响 spastin 水平。ETS（E 二十六个特异性）-结构域转录因子 Elk1 已被证明对突触可塑性很重要，并与微管相互作用。在这项研究中，我们旨在确定 SPG4 基因的关键启动子区域以及 Elk 对 SPG4 基因表达的影响。我们确定了 700bp 的无 TATA 启动子，包括一个关键的 CpG 岛作为最优启动子，CpG 岛缺失逐渐降低了 SPG4 启动子活性。此外，我们通过 EMSA 确定了 Elk1 在 SPG4 启动子上的结合位点。Elk1 的过表达表明它抑制了 SPG4 启动子，也降低了 SHSY-5Y 细胞中的 spastin 蛋白水平。
