Transient failure to dephosphorylate the cdc2-cyclin B1 complex accompanies radiation-induced G{sub 2}-phase arrest in HeLa cells
- Harvard School of Public Health, Boston, MA (United States)
Ionizing radiation causes a division delay in mammalian cells, dominated by a period of G{sub 2}-phase arrest. The G{sub 2}- to M-phase transition in dividing mammalian cells is dependent on the kinase activity of the cdc2-cyclin B protein complex. In the present investigation we measured the quantities of these two proteins, the formation of their complex and the kinase activity of the complex as a function of cell age in the cell cycle for irradiated and control mammalian cell populations. The human HeLa S3 cells were synchronized at the G{sub 1}/S-phase border by double thymidine block and exposed 3 h after release to 1.75 Gy of X rays. Studies of HeLa cells at other laboratories have shown that, for doses of 5 Gy or more, division delay is associated with a suppression of production of cyclin B mRNA. Here we report that, for cells irradiated with low doses, there is a transient failure of the complex to activate which correlates with the duration of radiation-induced G{sub 2}-phase arrest. The irradiated cells showed an increase in both cyclin B and phosphorylated cdc2 over the levels in control cells, and both persisted for a much longer period than in controls, further confirmation of delay in the activation of the catalytic subunit. 31 refs., 6 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 146886
- Journal Information:
- Radiation Research, Journal Name: Radiation Research Journal Issue: 3 Vol. 143; ISSN RAREAE; ISSN 0033-7587
- Country of Publication:
- United States
- Language:
- English
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