Wystub S, Ebner B, Fuchs C, Weich B, Burmester T, Hankeln T
Institute of Molecular Genetics and Institute of Zoology, Johannes Gutenberg University Mainz, Mainz, Germany.
Cytogenet Genome Res. 2004;105(1):65-78. doi: 10.1159/000078011.
Neuroglobin and cytoglobin are two novel members of the vertebrate globin family. Their physiological role is poorly understood, although both proteins bind oxygen reversibly and may be involved in cellular oxygen homeostasis. Here we investigate the selective constraints on coding and non-coding sequences of the neuroglobin and cytoglobin genes in human, mouse, rat and fish. Neuroglobin and cytoglobin are highly conserved, displaying very low levels of non-synonymous nucleotide substitutions. An oxygen supply function predicts distinct modes of gene regulation, involving hypoxia-responsive transcription factors. To detect conserved candidate regulatory elements, we compared the neuroglobin and cytoglobin genes in mammals and fish. The myoglobin gene was included to test if it also contains hypoxia-responsive regulatory elements. Long conserved non-coding sequences, indicative of gene-regulatory elements, were found in the cytoglobin and myoglobin, but not in the neuroglobin gene. Sequence comparison and experimental data allowed us to delimit upstream regions of the neuroglobin and cytoglobin genes that contain the putative promoters, defining candidate regulatory regions for functional tests. The neuroglobin and the myoglobin genes both lack conserved hypoxia-responsive elements (HREs) for transcriptional activation, but contain conserved hypoxia-inducible mRNA stabilization signals in their 3' untranslated regions. The cytoglobin gene, in contrast, harbors both conserved HREs and mRNA stabilization sites, strongly suggestive of an oxygen-dependent regulation.
神经球蛋白和细胞球蛋白是脊椎动物球蛋白家族的两个新成员。尽管这两种蛋白质都能可逆地结合氧气并可能参与细胞氧稳态，但它们的生理作用仍知之甚少。在这里，我们研究了人类、小鼠、大鼠和鱼类中神经球蛋白和细胞球蛋白基因的编码和非编码序列上的选择限制。神经球蛋白和细胞球蛋白高度保守，非同义核苷酸替换水平极低。氧气供应功能预示着不同的基因调控模式，涉及缺氧反应转录因子。为了检测保守的候选调控元件，我们比较了哺乳动物和鱼类中的神经球蛋白和细胞球蛋白基因。纳入肌红蛋白基因以测试其是否也含有缺氧反应调控元件。在细胞球蛋白和肌红蛋白中发现了指示基因调控元件的长保守非编码序列，但在神经球蛋白基因中未发现。序列比较和实验数据使我们能够划定神经球蛋白和细胞球蛋白基因包含推定启动子的上游区域，确定用于功能测试的候选调控区域。神经球蛋白和肌红蛋白基因都缺乏用于转录激活的保守缺氧反应元件（HREs），但在其3'非翻译区含有保守的缺氧诱导mRNA稳定信号。相比之下，细胞球蛋白基因既含有保守的HREs又含有mRNA稳定位点，强烈暗示其存在氧依赖性调控。
