Expression of cyclin (PCNA) and the phosphoprotein dividin are late obligatory events in the mitogenic response.

Analysis of the overall patterns of gene expression at the polypeptide synthesis level has revealed two S-phase specific, proliferation sensitive nuclear proteins [cyclin (PCNA) and dividin (phosphoprotein)] whose rate of synthesis increases at the G1/S transition border of the cell cycle. All available evidence suggests that expression of these proteins are late obligatory events in the mitogenic response.