Jeserich G, Strelau J, Lanwert C
University of Osnabrück, Department of Animal Physiology, Germany.
J Neurosci Res. 1997 Dec 1;50(5):781-90. doi: 10.1002/(SICI)1097-4547(19971201)50:5<781::AID-JNR14>3.0.CO;2-4.
The IP gene of trout encodes two Po-like glycoproteins which are expressed by oligodendrocytes in the fish CNS. A 679 bp fragment of its 5'-flanking region was isolated from a genomic library and sequenced. The transcription start point was determined 124 bp upstream the ATG initiator codon by primer extension analysis. Apart from a modified TATA-box and an inverted CCAAT-box located at canonical distances from the transcription start site several eucaryotic cis-acting regulatory elements were identified in the 679 bp upstream region, including an AP-1 binding site, a brain specific Sp1 motif, a cyclic AMP responsive element and a consensus sequence for POU homeodomain protein binding. The occurence of respective DNA-binding proteins for Sp1, AP-1 and POU in the nuclei of trout oligodendrocyte progenitor cells was verified by gel retardation experiments. Functional activity of various subfragments of the 679 bp upstream region was demonstrated by CAT reporter gene analysis. A computer-assisted sequence alignment of the trout IP 5'-flanking end with the corresponding region of the mammalian PLP gene promoter revealed four sites of high homology, while similarity with the mammalian Po gene promotor was low. The results are discussed with respect to the phylogenetic shift from Po-like proteins to PLP during evolution of the vertebrate CNS myelin sheath.
鳟鱼的IP基因编码两种Po样糖蛋白，它们由鱼类中枢神经系统中的少突胶质细胞表达。从基因组文库中分离出其5'侧翼区的一个679 bp片段并进行测序。通过引物延伸分析确定转录起始点位于ATG起始密码子上游124 bp处。除了位于距转录起始位点标准距离处的一个修饰的TATA盒和一个反向CCAAT盒外，在679 bp上游区域还鉴定出几个真核顺式作用调控元件，包括一个AP-1结合位点、一个脑特异性Sp1基序、一个环磷酸腺苷反应元件和一个POU同源结构域蛋白结合的共有序列。通过凝胶阻滞实验证实了鳟鱼少突胶质细胞祖细胞核中存在与Sp1、AP-1和POU相应的DNA结合蛋白。通过CAT报告基因分析证明了679 bp上游区域各个亚片段的功能活性。鳟鱼IP 5'侧翼末端与哺乳动物PLP基因启动子相应区域的计算机辅助序列比对显示有四个高度同源位点，而与哺乳动物Po基因启动子的相似性较低。结合脊椎动物中枢神经系统髓鞘在进化过程中从Po样蛋白到PLP的系统发育转变对结果进行了讨论。
