Induction of dystrophin Dp71 expression during neuronal differentiation: opposite roles of Sp1 and AP2α in Dp71 promoter activity

In this study, we delineated the molecular mechanisms that modulate Dp71 expression during neuronal differentiation, using the N1E‐115 cell line. We demonstrated that Dp71 expression is up‐regulated in response to cAMP‐mediated neuronal differentiation of these cells, and that this induction is controlled at promoter level. Functional deletion analysis of the Dp71 promoter revealed that a 5′‐flanking 159‐bp DNA fragment that contains Sp1 and AP2 binding sites is necessary and sufficient for basal expression of this TATA‐less promoter, as well as for its induction during neuronal differentiation. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed that Sp1 and AP2α bind to their respective DNA elements within the Dp71 basal promoter. Overall, mutagenesis assays on the Sp1 and AP2 binding sites, over‐expression of Sp1 and AP2α, as well as knock‐down experiments on Sp1 and AP2α gene expression established that Dp71 basal expression is controlled by the combined action of Sp1 and AP2α, which act as activator and repressor, respectively. Furthermore, we demonstrated that induction of Dp71 expression in differentiated cells is the result of the maintenance of positive regulation exerted by Sp1, as well as of the loss of AP2α binding, which ultimately releases the promoter from repression.     

构建来自宫颈癌并带有突变及缺失LCR的HPV16重组体

为研究ＨＰＶ１６转录调节蛋白ＹＹ１结合位点改变对病毒致癌性的影响,以ＨＰＶ１６野毒株质粒ｐ１２０３为基础,经多次克隆,将来自宫颈癌组织并带有缺损突变的ＬＣＲ重组到地ＨＰＶ１６基因组中。核酸序列分析证实,质粒ｐＤＶ３９０在第２个ＹＹ１位点上有一Ｇ→Ａ点穷变,质粒ｐＤＶ３２６和ｐＤＶ４０１分别带有１１５ｂｐ和１４３ｂｐ的缺失突变,从而涉及２和４个ＹＹ１结合位点,重组质粒其它核苷酸序列与ＨＰＶ１６标准序列一致。这些重组质粒的组建为进一步研究ＹＹ１蛋白对ＨＰＶ１６致癌基因表达的调控及ＨＰＶ１６致癌作用的影响打下基础。     

Genomic structure and promoter analysis of the mouse neutral ceramidase gene

We report here the molecular cloning of the mouse neutral ceramidase gene and its promoter analysis. The gene, composed of 27 exons ranging in size from 40 to 292 bp, spans more than 70 kb. Analysis of the 5(')-flanking region of the ceramidase genes revealed that the first exon of the gene of mouse liver was exactly the same as that of mouse kidney and Swiss 3T3 fibroblasts but completely different from that of mouse brain. The putative promoter regions of liver and brain ceramidase genes contained several well-characterized promoter elements such as GATA-2, C/EBP, and HNF3beta but lacked TATA and CAAT boxes, a typical feature of a housekeeping gene, although the expression is regulated in a tissue-specific manner. Interestingly, a GC box was exclusively found in the putative promoter of mouse liver whereas potential AP1 and AP4 binding sites were present in that of mouse brain. By a luciferase reporter gene assay, it was shown that the GC-rich region, which exists just upstream of the first exon, conferred the promoter activity in Swiss 3T3 cells.