Microinjected c-myc as a competence factor.
While a number of oncogenes are expressed in a cell cycle-dependent manner, their role in the control of cell proliferation can only be established by a direct functional assay. The c-myc protein, upon microinjection into nuclei of quiescent Swiss 3T3 cells, cooperated with platelet-poor plasma in the stimulation of cellular DNA synthesis. This suggests that c-myc protein, like platelet-derived growth factor (PDGF), may act as a competence factor in the cell cycle to promote the progression of cells to S phase. The presence in the medium of an antibody against PDGF abolished DNA synthesis induced by microinjected PDGF; however, the microinjected c-myc protein stimulated DNA synthesis even when its own antibody was present in the medium. The c-myc protein may act as an intracellular competence factor, while PDGF expresses its biological activity only from outside the cells.
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D051379:Mice; D009857:Oncogenes; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology
D010982:Platelet-Derived Growth Factor; D004247:DNA