Zhang Wei, Tian Zhipeng, Sha Sha, Cheng Lydia Yuk Luen, Philipsen Sjaak, Tan-Un Kian-Cheng
School of Biological Sciences, The University of Hong Kong, Hong Kong SAR.
Biochim Biophys Acta. 2011 Apr-Jun;1809(4-6):236-44. doi: 10.1016/j.bbagrm.2011.02.003. Epub 2011 Mar 9.
Neuroglobin (Ngb), a recently found oxygen-binding protein belonging to the vertebrate globin family, is mainly expressed in neurons of brains and eyes. Current studies have revealed diverse potential functions of Ngb and it was found to be able to reduce the severity of stroke and Alzheimer's disease, implying its importance in brains. However, the mechanism of Ngb regulation of transcription has not been elucidated yet. In this study, we analyzed the 5'-flanking region of human neuroglobin gene (NGB) and identified a transcription start site (TSS) located at -306bp relative to the translation start site ATG. We characterized the proximal promoter of NGB and found two GC-boxes located at -16 and +30bp relative to the TSS which are bound by transcription factor Sp1 and Sp3. Mutation of either GC-box led to a significant reduction in NGB promoter activity, while overexpression of Sp1 and Sp3 resulted in activation of the promoter. However, two putative NRSE sites (-359 and -127bp relative to the TSS) apparently showed no influence on NGB tissue-specific expression. Treatment of two non-neuronal cell lines HeLa and BEAS-2B with 5-aza-2'-deoxycytidine remarkably induced NGB expression, suggesting a potential role of DNA methylation in regulating NGB tissue-specific expression.
神经球蛋白（Ngb）是最近发现的一种属于脊椎动物球蛋白家族的氧结合蛋白，主要在大脑和眼睛的神经元中表达。目前的研究揭示了Ngb的多种潜在功能，并且发现它能够减轻中风和阿尔茨海默病的严重程度，这暗示了它在大脑中的重要性。然而，Ngb调节转录的机制尚未阐明。在本研究中，我们分析了人类神经球蛋白基因（NGB）的5'侧翼区域，并确定了一个相对于翻译起始位点ATG位于-306bp处的转录起始位点（TSS）。我们对NGB的近端启动子进行了表征，发现相对于TSS在-16和+30bp处有两个GC盒，它们与转录因子Sp1和Sp3结合。任一GC盒的突变都会导致NGB启动子活性显著降低，而Sp1和Sp3的过表达则会导致启动子激活。然而，两个假定的NRSE位点（相对于TSS为-359和-127bp）显然对NGB组织特异性表达没有影响。用5-氮杂-2'-脱氧胞苷处理两种非神经元细胞系HeLa和BEAS-2B可显著诱导NGB表达，这表明DNA甲基化在调节NGB组织特异性表达中可能起作用。
