Assignment of SV40-immortalized cells to more than one complementation group for immortalization.

Human cell lines have been assigned to four complementation groups for immortalization [O.M. Pereira-Smith and J. R. Smith, Proc. Natl. Acad. Sci. USA 85, 6042-6046, 1988]. Three SV40-immortalized epithelial cell lines were fused to cell lines representative of each of these four complementation groups. All three formed senescent hybrids with an SV40-immortalized cell line representative of group A, indicating that SV40 genes do not always cause immortalization via the same genetic mechanism. In contrast to the results of studies with other human cell lines, each of these three cell lines was assigned to more than one complementation group for immortalization. Thus these cell lines may have lost the function of two or more putative senescence genes.