Thomson T M, Green S H, Trotta R J, Burstein D E, Pellicer A
Department of Pathology, New York University Medical Center, New York 10016.
Mol Cell Biol. 1990 Apr;10(4):1556-63. doi: 10.1128/mcb.10.4.1556-1563.1990.
A cell line was generated from U7 cells (a subline of PC12 rat pheochromocytoma cells) that contains a stably integrated transforming mouse N-ras (Lys-61) gene under the control of the long terminal repeat from mouse mammary tumor virus. Such cells, designated UR61, undergo neuronal differentiation upon exposure to nanomolar concentrations of dexamethasone, as a consequence of expression of the activated N-ras gene (I. Guerrero, A. Pellicer, and D.E. Burstein, Biochem, Biophys. Res. Commun. 150:1185-1192, 1988). Exposure of UR61 cells to either nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) results in a marked induction of c-fos RNA, with kinetics paralleling those of NGF- or bFGF-induced expression of c-fos RNA in PC12 cells. Dexamethasone-induced expression of activated N-ras p21 results in blocking of c-fos RNA induction by NGF or bFGF in a time-dependent manner. Activated N-ras p21-mediated inhibition of c-fos RNA induction in UR61 cells is selective for NGF and bFGF and is not due to selective degradation of c-fos RNA. Normal and transforming N-ras can trans activate the chloramphenicol acetyltransferase gene linked to mouse c-fos regulatory sequences when transient expression assays are performed. Our observations suggest that N-ras p21 selectively interacts with pathways involved in induction of c-fos expression which initiate at the receptors for NGF and bFGF.
从U7细胞（PC12大鼠嗜铬细胞瘤细胞的一个亚系）中构建了一个细胞系，该细胞系含有在小鼠乳腺肿瘤病毒长末端重复序列控制下稳定整合的转化型小鼠N-ras（Lys-61）基因。这种细胞命名为UR61，在暴露于纳摩尔浓度的地塞米松后会发生神经元分化，这是活化的N-ras基因表达的结果（I. Guerrero、A. Pellicer和D.E. Burstein，《生物化学与生物物理学研究通讯》150:1185 - 1192，1988）。将UR61细胞暴露于神经生长因子（NGF）或碱性成纤维细胞生长因子（bFGF）会导致c-fos RNA的显著诱导，其动力学与PC12细胞中NGF或bFGF诱导的c-fos RNA表达的动力学相似。地塞米松诱导的活化N-ras p21表达会以时间依赖性方式阻断NGF或bFGF对c-fos RNA的诱导。活化的N-ras p21介导的UR61细胞中c-fos RNA诱导的抑制对NGF和bFGF具有选择性，并非由于c-fos RNA的选择性降解。当进行瞬时表达分析时，正常和转化型N-ras都可以反式激活与小鼠c-fos调控序列相连的氯霉素乙酰转移酶基因。我们的观察结果表明，N-ras p21与参与c-fos表达诱导的途径选择性相互作用，这些途径从NGF和bFGF的受体开始。
