Functional and sequence analysis of human neuroglobin gene promoter region

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 − 306 bp relative to the translation start site ATG. We characterized the proximal promoter of NGB and found two GC-boxes located at − 16 and + 30 bp 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 − 127 bp 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.

Research highlights
► One transcription start site of human neuroglobin (NGB) locates at −306 bp relative to the translation start codon ATG.
► The proximal promoter of NGB lies between −164 to + 306 bp relative to the transcription start site of NGB.
► Both Sp1 and Sp3 are transactivators of NGB.
► Treatment of HeLa and BEAS-2B with 5-aza-2′-deoxycytidine induces NGB transcription.