The expression of plasminogen activator in rous sarcoma virus-transformed cells is controlled both by the virus and the cell

Abstract

Virus produced by clones of Rous sarcoma virus-transformed chicken embryo fibroblasts was analyzed for the ability to elevate the level of the cellular plasminogen activator upon transformation of cells using a casein-plaque assay. Virus from clones exhibiting low levels of plasminogen activator was not defective in its ability to produce foci of transformed cells with increased levels of plasminogen activator assayed by casein-plaque formation. Superinfection of low plasminogen activator clones with another strain of Rous sarcoma virus increased the level of plasminogen activator expressed by these cells. These results suggest that the level of plasminogen activator expressed by a transformed cell is determined predominantly by the cell type, but is also influenced by the presence of the src gene of Rous sarcoma virus.