Ehretsmann C P, Chandler L A, Bourgeois S
Salk Institute for Biological Studies, Regulatory Biology Laboratory, San Diego, CA 92186-5800, USA.
Mol Cell Endocrinol. 1995 Apr 28;110(1-2):185-94. doi: 10.1016/0303-7207(95)03531-b.
Treatment of the human fibrosarcoma cell line HT-1080 with glucocorticoids results in the induction of fibronectin (FN) protein and mRNA synthesis. We tested the contribution of transcriptional and post-transcriptional mechanisms in the regulation of FN by the synthetic glucocorticoid dexamethasone (DEX). Using nuclear run-on experiments, we found that the DEX-dependent induction of FN occurs primarily at the post-transcriptional level. The half-life of total FN mRNA was not affected by hormone treatment indicating that the induction of FN gene expression is not due to stabilization of the mature message. Interestingly, the induction by DEX was present at the level of nuclear FN RNA. We found that polyadenylation and alternative splicing of the ED-B domain of the FN transcript were not affected by glucocorticoid treatment. However, DEX was found to increase the steady-state level of unspliced FN transcript. Our data indicate that DEX exerts its effect on FN expression predominantly at the post-transcriptional level by a mechanism that, unlike most examples of post-transcriptional regulation by glucocorticoids, acts in the nucleus. Furthermore, they suggest that glucocorticoids activate a mechanism to stabilize the unspliced FN RNA. In an attempt to localize the FN RNA sequences mediating the DEX-dependent induction, we performed transfection analyses of FN minigene constructs. We suggest that the DEX-dependent regulatory elements are located in the introns since no such elements were found in the 8 kb FN mRNA.
用糖皮质激素处理人纤维肉瘤细胞系HT - 1080会诱导纤连蛋白（FN）蛋白和mRNA的合成。我们测试了合成糖皮质激素地塞米松（DEX）在转录和转录后机制对FN调控中的作用。通过核转录实验，我们发现DEX依赖的FN诱导主要发生在转录后水平。总FN mRNA的半衰期不受激素处理的影响，这表明FN基因表达的诱导不是由于成熟mRNA的稳定。有趣的是，DEX诱导在核FN RNA水平上存在。我们发现FN转录本ED - B结构域的聚腺苷酸化和可变剪接不受糖皮质激素处理的影响。然而，发现DEX会增加未剪接的FN转录本的稳态水平。我们的数据表明，DEX主要通过一种不同于糖皮质激素转录后调控大多数例子的机制在转录后水平上对FN表达发挥作用，该机制在细胞核中起作用。此外，它们表明糖皮质激素激活了一种稳定未剪接的FN RNA的机制。为了定位介导DEX依赖诱导的FN RNA序列，我们对FN小基因构建体进行了转染分析。我们认为DEX依赖的调控元件位于内含子中，因为在8 kb的FN mRNA中未发现此类元件。
