Shastry B S
Eye Research Institute, Oakland University, Rochester, Michigan 48309.
Arch Biochem Biophys. 1993 Nov 1;306(2):476-85. doi: 10.1006/abbi.1993.1540.
In an attempt to understand the molecular mechanisms governing the cell-type-specific expression of human gamma crystallin genes we have analyzed human lens extract for the presence of factors which specifically interact with the regulatory regions. Our analyses indicate that a partially purified fraction contains an activity which specifically recognizes the proximal domain (-46 to -26) of the human gamma crystallin gene. This conserved region has been previously shown to function as a strong transcriptional activator of the mouse gamma crystallin gene. Methylation interference experiments further suggest that the factor makes contact with several G residues within this protected region. A similar (but not necessarily identical) activity is also found to be present in HeLa cell, lens epithelial cell and retinal pigment epithelial cell extracts. However, no such activity is detectable in nonlens fibroblast extract. Further characterization of the proteins reveals that the lens factor differs in its physical properties from that of the HeLa factor. These results demonstrate the presence of a candidate regulatory factor(s) in human lens which may be directly or indirectly involved in modulating the tissue-specific expression of the human gamma crystallin gene.
为了了解调控人类γ-晶体蛋白基因细胞类型特异性表达的分子机制，我们分析了人晶状体提取物中是否存在与调控区域特异性相互作用的因子。我们的分析表明，一个部分纯化的组分含有一种活性，该活性能特异性识别人类γ-晶体蛋白基因的近端结构域（-46至-26）。先前已表明，这个保守区域可作为小鼠γ-晶体蛋白基因的强转录激活因子发挥作用。甲基化干扰实验进一步表明，该因子与这个受保护区域内的几个鸟嘌呤残基发生接触。在HeLa细胞、晶状体上皮细胞和视网膜色素上皮细胞提取物中也发现了类似（但不一定相同）的活性。然而，在非晶状体成纤维细胞提取物中未检测到这种活性。对这些蛋白质的进一步表征表明，晶状体因子的物理性质与HeLa因子不同。这些结果证明了人晶状体中存在一种候选调控因子，它可能直接或间接参与调节人类γ-晶体蛋白基因的组织特异性表达。
