Assignment of gene(s) for cell transformation to human chromosome 7 carrying the simian virus 40 genome.

Somatic cell hybrid clones between either C57BL/6 or Balb/c mouse peritoneal macrophages and two different simian virus 40 (SV40)-transformed human cell lines deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase) were obtained in hypoxanthine-aminopterin-thymidine selective medium. All the hybrid cell clones contained the human chromosome 7, which carries the SV40 genome, and were SV40 tumor (T)-antigen positive. No hybrid cell clones studied displayed the density-dependent inhibition of cell growth characteristic of normal cells; all clones had a high saturation density and gave origin to cell colonies when plated in soft agar. Since the expression of the transformed phenotype was always associated with the presence of the human chromosome 7, which carries the SV40 genome, it is concluded that this chromosome contains gene(s) [Tr gene(s)] coding for "transforming factor(s)."