Reinitiation of DNA synthesis in senescent human fibroblasts upon fusion with cells of unlimited growth potential

Postreplicative, "senescent" human fibroblasts were fused to HeLa or to SV-40 transformed human fibroblasts with Sendai virus. DNA synthesis was reinitiated in senescent nuclei in a high proportion of the heterodikaryons. The 3H]thymidine labeling index of senescent fibroblast nuclei in heteropolykaryons was a function of the ratio of HeLa to senescent nuclei.