Modulation of pp60v-src and pp60c-src expression in Rous sarcoma virus-transformed hamster fibroblasts transfected with activated N-ras

• Published in: Molecular carcinogenesis Vol. 8; no. 3; p. 167
• Main Authors: 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
• Format: Journal Article
• Language: English
• Published: United States 1993
• Subjects: Animals; Avian Sarcoma Viruses; Cell Transformation, Viral; Cells, Cultured; Cricetinae; Gene Expression Regulation; Genes, ras; Immunoblotting; Oncogene Protein pp60(v-src) - metabolism; Transfection
• ISSN: 0899-1987
• 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.