Molecular analysis of H2O2-induced senescent-like growth arrest in normal human fibroblasts: p53 and Rb control G1 arrest but not cell replication.

摘要: Human diploid fibroblasts lose the capacity to proliferate and enter a state termed replicative senescence after finite number of cell divisions in culture. When treated with sub-lethal concentrations H2O2, pre-senescent human long-term growth arrest resembling senescence. To understand molecular basis for H2O2-induced arrest, we determined cycle distribution, levels p53 tumour suppressor p21 cyclin-dependent kinase inhibitor proteins, status Rb phosphorylation H2O2-treated cells. A 2-h pulse H2O2 arrested IMR-90 fetal lung at least 15 days. The cells showed G1 DNA content. level protein increased 2- 3-fold within 1.5 h exposure but returned control by 48 h. induction was dose dependent, beginning 50-75 microM reaching maximum 100-250 microM. did not appear correlate damage as measured formation 8-oxo-2'-deoxyguanosine DNA. about 18 remained elevated 21 During this period, underphosphorylated. abolished iron chelator deferoxamine synthesis cycloheximide. papillomavirus E6, when introduced into cells, p53, reduced minimal allowed entry S-phase. E7 overall also arrest. Inactivating or both restore ability Thus show transient elevation high p21, lack phosphorylation, inability replicate is inactivated.