Human endothelial cell lines established by mutated forms of the simian virus 40 large T oncogene

The large T oncoprotein of Simian Virus 40 is widely used to improve the growth characteristics of primary cells in culture. Beside growth stimulation and immortalization, expression of the large T protein in human cells frequently leads to a loss of differentiated characters and changes in the karyotype. We have constructed mutated forms of the large T protein by deletion of various fragments of the DNA binding domain to test, whether this region is responsible for undesired influences on cell differentiation. After transfection into human umbilical vein endothelial cells, the resulting cell lines showed no improvement in expression of the differentiation marker von Willebrand factor compared to cell lines transfected with the wild type oncogene. Changes in the karyotype were still observed. Our results contribute to the mapping of functional domains of the large T protein. The truncated large T proteins retained growth stimulating activity after removal of 111 and 241 amino acids of the DNA binding region.