Effects of caffeine on protein phosphorylation and cell cycle progression in X-irradiated two-cell mouse embryos.
The G2 phase/mitosis transition in cleavage-stage mouse embryos is correlated with an increased phosphorylation of a defined set of proteins at 46, 35, 30, and 29 kDa. Cell cleavage and the associated changes in protein phosphorylation are delayed after X-irradiation. To understand the mechanism of the caffeine-induced uncoupling of mitosis and the cellular reactions to DNA-damaging agents, we have studied the effects of caffeine treatment on cell cycle progression and protein phosphorylation in two-cell mouse embryos after X-irradiation. Caffeine alone had no effect on timing of and changes in phosphorylation associated with the embryonic cell cycle. In combination with X-rays, however, caffeine was able to override the radiation induced G2 block and restored the normal timing of these phosphorylation changes after X-irradiation. However, new additional changes in protein phosphorylation appeared after the combined treatment. Isobutylmethylxanthine (IBMX), a substance chemically related to caffeine but a more specific inhibitor of the phosphodiesterase that breaks down cyclic AMP, reduced the radiation induced G2 block from 4 to 5 h to about 1 h and restored the cell cycle associated changes in protein phosphorylation. However, the same new changes which appeared after the combined treatment of caffeine and X-rays were observed after the combination of IBMX and X-irradiation. IBMX specific changes in protein phosphorylation were detected in both the single and the combined treatment. These results indicate a similar action of caffeine and IBMX in overriding the radiation induced G2 block in two-cell mouse embryos.
Jung
T
T
Department of Molecular Embryology, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, UK.
Streffer
C
C
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D004622:Embryo, Mammalian / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011506:Proteins / Q000378:metabolism*
D011506:Proteins; D002110:Caffeine