Koh J, Sferra T J, Collins F S
Department of Human Genetics, University of Michigan, Ann Arbor 48109-0650.
J Biol Chem. 1993 Jul 25;268(21):15912-21.
Expression of the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) is tightly regulated. Using a panel of cell lines expressing different levels of CFTR mRNA, we investigated the mechanisms mediating control of CFTR transcription. In highly expressing cells, multiple sites of transcription initiation can be identified between positions -95 and +50 of the CFTR gene, and an alternatively initiated splice variant transcript is also present. Nonepithelial cell lines expressing very low levels of CFTR utilize a start site at -32. Promoter sequence elements from -83 to +111 are at least partially responsible for dictating CFTR transcriptional tissue-specificity, while multiple elements located farther 5' augment promoter strength. Analysis of the chromatin structure and methylation status of the CFTR promoter region reveals cell line differences which correlate with expression levels, suggesting that the physical context of the CFTR gene in vivo may contribute significantly to appropriate regulation of CFTR transcription. Taken together, these findings indicate that cellular control of CFTR gene expression is likely to be a complex function of several overlapping regulatory pathways.
编码囊性纤维化跨膜传导调节因子（CFTR）的基因表达受到严格调控。我们使用一组表达不同水平CFTR mRNA的细胞系，研究了介导CFTR转录调控的机制。在高表达细胞中，可在CFTR基因-95至+50位之间鉴定出多个转录起始位点，并且还存在一种选择性起始的剪接变体转录本。表达极低水平CFTR的非上皮细胞系利用-32位的起始位点。从-83至+111的启动子序列元件至少部分负责决定CFTR转录的组织特异性，而位于更上游5'端的多个元件增强启动子强度。对CFTR启动子区域的染色质结构和甲基化状态分析揭示了与表达水平相关的细胞系差异，这表明CFTR基因在体内的物理环境可能对CFTR转录的适当调控有显著贡献。综上所述，这些发现表明CFTR基因表达的细胞调控可能是几种重叠调控途径的复杂功能。
