Gaiddon C, Boutillier A L, Monnier D, Mercken L, Loeffler J P
Institut de Physiologie et de Chimie Biologique, URA 1446 du CNRS, Strasbourg, France.
J Biol Chem. 1994 Sep 9;269(36):22663-71.
Somatic mutations of the alpha subunit of Gs (G alpha s) have been detected in a variety of endocrine tumors. To test whether G alpha s is an oncogene, we investigated the genomic effects of G alpha s protein in which the GTPase activity had been inactivated. Results from transient transfection studies show that such proteins increase 1) transcription of a reporter gene driven by the minimal cAMP-responsive element (TGACGTCA) and 2) c-fos transcription in several endocrine cell lines (GH3, AtT20, and PC12). By promoter deletion analyses and genetic inactivation of cAMP-dependent protein kinase, we show that this transcriptional stimulation by G alpha s impinges on several regulatory elements within the c-fos promoter and operates within the protein kinase A pathways. Stable PC12 cell lines were established to analyze long-term effects of constitutively active G alpha s. Cell lines expressing mutated G alpha s have elevated cAMP levels and increased AP1 binding activity. Transcription of a variety of genes, including c-fos, c-jun, and junB, is increased in these cells. The strong and permanent effects of G alpha s on early immediate genes, and c-fos in particular, may be responsible for the oncogenic potential of G alpha s in endocrine cells.
在多种内分泌肿瘤中已检测到Gs的α亚基（Gαs）的体细胞突变。为了测试Gαs是否为癌基因，我们研究了GTP酶活性已失活的Gαs蛋白的基因组效应。瞬时转染研究结果表明，此类蛋白可增强：1）由最小cAMP反应元件（TGACGTCA）驱动的报告基因的转录，以及2）几种内分泌细胞系（GH3、AtT20和PC12）中的c-fos转录。通过启动子缺失分析和cAMP依赖性蛋白激酶的基因失活，我们表明Gαs的这种转录刺激作用于c-fos启动子内的多个调控元件，并在蛋白激酶A途径内发挥作用。建立了稳定的PC12细胞系以分析组成型活性Gαs的长期效应。表达突变型Gαs的细胞系具有升高的cAMP水平和增强的AP1结合活性。这些细胞中包括c-fos、c-jun和junB在内的多种基因的转录均增加。Gαs对早期即刻基因，尤其是c-fos的强烈而持久的影响，可能是Gαs在内分泌细胞中具有致癌潜力的原因。
