Transformation of NIH3T3 cells by Rous sarcoma virus occurs with high efficiency in the absence of proviral rearrangements or amplification.
NIH3T3 cells could be transformed by a mammaltropic strain of Rous sarcoma virus (RSV) with an efficiency 10(3) times greater than that observed in Balb/c 3T3 cells or other mammalian cell lines and almost identical to that of chick embryo fibroblasts. In infected NIH3T3 cells a single, properly integrated, provirus was sufficient to induce focus formation; moreover, kinase activity of pp60v-src and tyrosine phosphorylation of cellular proteins could be detected very soon after infection in the majority of cells. On the other hand, in transformed foci from RSV-infected Balb/c 3T3 cells both rearrangements and amplification of proviral sequences were frequently detected. Accordingly, expression of pp60v-src and ensuing tyrosine phosphorylation of cellular proteins occurred, at high levels, only in a minority of the infected cells. Furthermore, by using a murine retrovirus carrying the v-src oncogene and an independent selectable marker, we found that Balb/c 3T3 cells were transformed with a 100-fold lower efficiency than NIH3T3 cells, yet the majority of infected untransformed Balb/c 3T3 cells expressed active pp60v-src. These findings are consistent with the existence in most mammalian cell lines of a major restriction to v-src-induced transformation, operating at the level of proviral expression, that is apparently absent in NIH3T3 cells.
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Istituto di Biologia Cellulare, Consiglio Nazionale delle Ricerche, Rome, Italy.
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Alemà
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D016475:3T3 Cells; D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics*; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D005784:Gene Amplification; D015321:Gene Rearrangement; D016391:Genes, src; D051379:Mice; D015688:Oncogene Protein pp60(v-src) / Q000032:analysis; D011533:Proviruses / Q000235:genetics*
D015688:Oncogene Protein pp60(v-src)