Persistence of the competent state in mouse fibroblasts is independent of c-fos and c-myc expression.

Induction of competence in quiescent fibroblasts by platelet-derived growth factor (PDGF) is accompanied by a dramatic increase in the expression of c-fos and c-myc genes. However, the maintenance of the competent state and progression through G1 does not require high expression of these proto-oncogenes. These results suggest that the induction of c-fos and c-myc by growth factors in quiescent fibroblasts may be required to render the cells competent for progression.