Topol L Z, Kisseljova N P, Gutierrez M L, Deichman G I, Musatkina E A, Shtutman M S, Zakamaldina T Z, Blair D G, Tatosyan A G
Laboratory of Molecular Oncology, National Cancer Institute, Frederick, Maryland 21702-1201.
Mol Carcinog. 1993;8(3):167-76. doi: 10.1002/mc.2940080307.
Three phenotypically different hamster cell lines transformed with Rous sarcoma virus (RSV) were transfected with plasmid DNA containing an activated N-ras oncogene, and nine clones expressing various levels of p21N-ras were characterized. We examined the effects of p21N-ras on expression and kinase activity of resident src proteins by using a variety of assays that allowed us to discriminate between viral and cellular src proteins. In eight clones with a 10- to 20-fold increase in p21N-ras levels relative to the endogenous protein, we observed a marked reduction in the synthesis and kinase activity of p60v-src. This decrease correlated with transcriptional downregulation of RSV genomic and v-src subgenomic mRNAs. In the same cells, we found a concomitant accumulation of p60c-src and, accordingly, an increase in its protein kinase activity without an apparent increase in c-src mRNA levels. Therefore, modulation of viral and cellular src proteins in cells overexpressing p21N-ras appeared to result from two distinct effects: a downregulation of long terminal repeat-driven transcription and a more complex interaction with cellular effectors that control the stability of p60c-src. Such modulation also seemed to depend on the levels of p21N-ras and, possibly, on host-cell factors, since it was not observed in the third cell line, in which the relative increase in p21N-ras was only 2.5-fold to fivefold.
用含有激活的N-ras癌基因的质粒DNA转染三种经劳氏肉瘤病毒（RSV）转化的表型不同的仓鼠细胞系，并对九个表达不同水平p21N-ras的克隆进行了表征。我们通过使用多种能够区分病毒和细胞src蛋白的检测方法，研究了p21N-ras对驻留src蛋白表达和激酶活性的影响。在八个相对于内源性蛋白p21N-ras水平增加10至20倍的克隆中，我们观察到p60v-src的合成和激酶活性显著降低。这种降低与RSV基因组和v-src亚基因组mRNA的转录下调相关。在相同的细胞中，我们发现p60c-src同时积累，因此其蛋白激酶活性增加，而c-src mRNA水平没有明显增加。因此，在过表达p21N-ras的细胞中，病毒和细胞src蛋白的调节似乎是由两种不同的效应导致的：长末端重复序列驱动的转录下调以及与控制p60c-src稳定性的细胞效应器更复杂的相互作用。这种调节似乎也取决于p21N-ras的水平，并且可能还取决于宿主细胞因子，因为在第三个细胞系中未观察到这种调节，在该细胞系中p21N-ras的相对增加仅为2.5倍至5倍。
