Lefevre C, Imagawa M, Dana S, Grindlay J, Bodner M, Karin M
EMBO J. 1987 Apr;6(4):971-81. doi: 10.1002/j.1460-2075.1987.tb04847.x.
The molecular basis for the pituitary-specific expression of the human growth hormone (hGH) gene was investigated, by gene transfer and protein footprinting experiments. Plasmid constructs in which CAT or Neo transcription units are fused to a 0.5 kb fragment of the hGH 5' sequences were efficiently expressed in GC and GH3 cells, derived from a pituitary tumor, but not in cell lines of other origins, indicating the presence of a tissue-specific promoter. DNaseI footprinting experiments have identified at least three factors that specifically bind to the hGH 5' region. While two of these factors were also detected in extracts of non-expressing cells, the third factor, GHF-1, was detected only in extracts of GH expressing pituitary tumor cells. Mutagenesis experiments suggest that binding of GHF-1 and some of the other more ubiquitous factors is required for optimal hGH promoter activity in vivo. Tissue specificity of the hGH promoter therefore seems to be determined by the binding of at least one tissue-specific trans-acting factor, acting in concert with several other more ubiquitous, yet specific, DNA binding proteins.
通过基因转移和蛋白质足迹实验，对人生长激素（hGH）基因垂体特异性表达的分子基础进行了研究。将CAT或Neo转录单位与hGH 5'序列的0.5 kb片段融合的质粒构建体，在源自垂体肿瘤的GC和GH3细胞中高效表达，但在其他来源的细胞系中不表达，这表明存在组织特异性启动子。DNaseI足迹实验已鉴定出至少三种与hGH 5'区域特异性结合的因子。虽然在非表达细胞的提取物中也检测到其中两种因子，但第三种因子GHF-1仅在表达hGH的垂体肿瘤细胞提取物中检测到。诱变实验表明，GHF-1和其他一些更普遍存在的因子的结合是体内hGH启动子最佳活性所必需的。因此，hGH启动子的组织特异性似乎是由至少一种组织特异性反式作用因子的结合所决定的，该因子与其他几种更普遍存在但具有特异性的DNA结合蛋白协同作用。
