ABSTRACT
Recent research on anti-oncogenes will certainly provide the strongest support for the hypothesis of negative growth control. However, in discussing normal growing cells vs. nongrowing cells, the authors focus on lines of evidence from cell fusion studies and unique nonproliferating-specific gene expression. A series of studies on heterokaryons, produced by fusion between senescent fibroblasts and their young counterparts or transformed derivatives, suggests that the cessation of proliferation in the former cells is controlled by “dominant factors”. This impression is based on the observation that in such hybrids, DNA synthesis in the replicating cells is turned off by factors associated with the nuclei of senescent fibroblasts. Ultrastructural localization by gold labeling shows that statin is specifically localized at the nuclear lamina region, facing the nucleoplasm. By manipulating the concentration of serum, one can regulate cells to stay in or leave the G0 growth block.
