An E2F site in the 5′‐promoter region contributes to serum‐dependent up‐regulation of the human proliferating cell nuclear antigen gene

The synthesis of proliferating cell nuclear antigen (PCNA) is strictly regulated during the cell cycle. To investigate the contribution of the promoter region to the up-regulation of human PCNA expression at the onset of S phase, we have examined 17 putative elements with reporter assays in quiescent L-O2 cells and following serum stimulation. The E2F-like sequence 5'-TTCCCCGCAA-3' located at -84 to -75 is required for the serum-induced transactivation. In electrophoretic mobility shift assays, nuclear extracts from asynchronous L-O2 cells exhibit two binding activities toward the -75 E2F oligonucleotide, and the minor band, whose formation could be interfered with by E2F-1 antibody, represents an S phase-specific complex. This is the first demonstration of the E2F site in the human PCNA 5' promoter as a serum-responsive element.