Foti D, Damante G, Rapoport B
Thyroid Molecular Biology Laboratory, University of California San Francisco, V.A. Medical Center 94121.
Cell Mol Biol. 1990;36(4):363-73.
TSH stimulates proliferation of FRTL5 rat thyroid cells, and also increases c-fos mRNA levels in these cells. We therefore investigated the role of c-fos in TSH-mediated FRTL5 cell proliferation. FRTL5 cells were stably transfected with plasmid constructs that transcribe, under the control of the dexamethasone-inducible MMTV promoter, a 5'-fragment (84 nucleotides) of c-fos mRNA, either in the sense or in the antisense orientation. Four c-fos antisense clones (A1, A2, A3, A4), one sense clone (S2), and wild-type (untransfected) FRTL5 cells were studied. Southern blot analysis indicated similar levels of transgenome in all transfected cell lines. Antisense clone A3 exhibited the greatest dexamethasone-induced growth inhibition, two times (59% vs. 30%) greater than that in control, sense c-fos-transfected or wild-type FRTL5, cells. Consistent with the degree of growth inhibition, northern blot analysis revealed that c-fos antisense clone A3 expressed the highest levels of c-fos antisense transcript. However, we did not observe dexamethasone induction of the antisense c-fos-beta globin hybrid mRNA in any clone, including clone A3. Taken together, our results provide circumstantial evidence that c-fos, at least in part, may play a role in TSH-mediated thyroid cell growth.
促甲状腺激素（TSH）可刺激FRTL5大鼠甲状腺细胞增殖，并增加这些细胞中c-fos mRNA的水平。因此，我们研究了c-fos在TSH介导的FRTL5细胞增殖中的作用。利用质粒构建体对FRTL5细胞进行稳定转染，该构建体在可被地塞米松诱导的小鼠乳腺肿瘤病毒（MMTV）启动子控制下，转录c-fos mRNA的5'片段（84个核苷酸），其方向可以是正义的，也可以是反义的。对四个c-fos反义克隆（A1、A2、A3、A4）、一个正义克隆（S2）以及野生型（未转染）FRTL5细胞进行了研究。Southern印迹分析表明，所有转染细胞系中的转基因水平相似。反义克隆A3表现出最大程度的地塞米松诱导的生长抑制，比对照、转染正义c-fos的细胞或野生型FRTL5细胞高出两倍（59%对30%）。与生长抑制程度一致，Northern印迹分析显示c-fos反义克隆A3表达的c-fos反义转录本水平最高。然而，我们在任何克隆中，包括克隆A3，均未观察到地塞米松诱导的反义c-fos-β珠蛋白杂交mRNA。综上所述，我们的结果提供了间接证据，表明c-fos至少在一定程度上可能在TSH介导的甲状腺细胞生长中发挥作用。
