Superti-Furga G, Bergers G, Picard D, Busslinger M
Institute of Molecular Pathology, Vienna, Austria.
Proc Natl Acad Sci U S A. 1991 Jun 15;88(12):5114-8. doi: 10.1073/pnas.88.12.5114.
The protooncogene c-fos has been implicated in the control of proliferation and transformation of fibroblasts, and its protein product is an essential component of transcription factor AP1. The important target genes and, hence, the molecular mechanism of Fos function are, however, still unknown, partly due to the lack of a tightly regulated Fos-induction system. Here we show that different activities of the Fos protein can be controlled hormonally by fusing the mouse c-Fos protein to the ligand-binding domain of either the rat glucocorticoid or the human estrogen receptor. These fusion proteins stimulate AP1-dependent transcription and repress endogenous fos mRNA synthesis in a strictly hormone-dependent manner. Expression of these chimeric proteins in rat fibroblasts results in fast, reversible, and tightly controlled transformation in response to hormone. A Fos-estrogen receptor expressing cell line was used to isolate Fos-responsive genes by subtractive cDNA cloning. Run-on analysis of one of these genes showed that its transcription is rapidly and directly regulated by the hormone-activated Fos-estrogen receptor protein, demonstrating the potential of this induction system for identifying Fos target genes.
原癌基因c-fos与成纤维细胞的增殖和转化调控有关，其蛋白质产物是转录因子AP1的重要组成部分。然而，Fos功能的重要靶基因以及分子机制仍不清楚，部分原因是缺乏严格调控的Fos诱导系统。在此我们表明，通过将小鼠c-Fos蛋白与大鼠糖皮质激素或人雌激素受体的配体结合域融合，Fos蛋白的不同活性可以受到激素调控。这些融合蛋白以严格的激素依赖方式刺激AP1依赖的转录并抑制内源性fos mRNA的合成。这些嵌合蛋白在大鼠成纤维细胞中的表达导致对激素快速、可逆且严格受控的转化。利用表达Fos-雌激素受体的细胞系，通过消减cDNA克隆分离Fos反应基因。对其中一个基因的连续分析表明，其转录受激素激活的Fos-雌激素受体蛋白快速且直接调控，证明了该诱导系统在鉴定Fos靶基因方面的潜力。
