Stimulation of protein accumulation in HeLa cells by inhibitors of DNA replication. Ferritin.

Incubation of HeLa cells for 24 h with either hydroxyurea (HU), aphidicolin (APHI), thymidine (T) or butyrate (BU), substances used to inhibit replication and accumulate cells at the G1/S interphase, followed by the elimination of the inhibitor and the addition of iron to the growth medium, results in an immediate (HU, APHI, T) or slightly delayed (BU) increased accumulation (18-24-fold higher than the basal level) of ferritin. Under the same experimental circumstances, 5-azacytidine is without effect. As a result of the action of these inhibitors on the structure of DNA, it is proposed that ferritin genes remain accessible to RNA polymerase allowing the accumulation in the cytoplasm of mature ferritin mRNA ready to be mobilized by iron for the production of ferritin molecules.