Peek R, Kraft H J, Klok E J, Lubsen N H, Schoenmakers J G
Department of Molecular Biology, University of Nijmegen, The Netherlands.
Nucleic Acids Res. 1992 Sep 25;20(18):4865-71. doi: 10.1093/nar/20.18.4865.
Rat lens nuclear extracts contain a factor that binds to position -57 to -46 of the rat gamma D-crystallin promoter region. This factor protects the sequence 5'-CTGCCAACGCAG-3' in a footprint analysis. Binding to this region is crucial for maximal promoter activity in rat lens cells, but this sequence was unable to act as an enhancer when cloned in front of a heterologous promoter. A region directly upstream from this activating sequence, between position -85 to -67, acts as a strong silencer of promoter activity in non-lens cells. This silencing effect is mediated by trans-acting factor(s). Our data provide evidence for two regulatory elements in rat gamma D-crystallin gene expression, an activating sequence active in lens cells and a silencing sequence active only in non-lens cells. The factor that binds to the activating sequence could be detected only in lens cells and may be a determinant of the lens-specific expression of the gamma-crystallin genes.
大鼠晶状体核提取物含有一种因子，它能与大鼠γD-晶状体蛋白启动子区域的-57至-46位结合。在足迹分析中，该因子可保护5'-CTGCCAACGCAG-3'序列。与该区域的结合对于大鼠晶状体细胞中的最大启动子活性至关重要，但当克隆到异源启动子前时，该序列无法发挥增强子的作用。此激活序列直接上游的一个区域，位于-85至-67位之间，在非晶状体细胞中作为启动子活性的强沉默子。这种沉默效应由反式作用因子介导。我们的数据为大鼠γD-晶状体蛋白基因表达中的两个调控元件提供了证据，一个是在晶状体细胞中活跃的激活序列，另一个是仅在非晶状体细胞中活跃的沉默序列。与激活序列结合的因子仅在晶状体细胞中可检测到，可能是γ-晶状体蛋白基因晶状体特异性表达的决定因素。
