Abstract: The cell proliferation of wild type KAx-3 and mutant type RNAi-allC observed by light microscope and cell counting, The latter was divided 8 time faste than the former. To evaluate the reason why RNAi-allC cell cycle shortened, the function of ATR-Chk1-Cdc25 signaling pathway were explored by quantitative PCR and western blot techniques. The results showed the differences of ATR, Chk1, Cdc25 in mRNA contents and protein level existed in KAx-3 and RNAi-allC cells, that is, the expression of ATR and Chk1 ratio of RNAi-allC to KAx-3 was 0.69〖DK〗∶1 and 0.1〖DK〗∶1 respectively; the expression of Cdc25 in RNAi-allC cells was 8 times that of KAx-3 cells. The data suggested that once the expression of ATR had little change, Chk1 and Cdc25 expression changed greatly. Western blotting results were consistent with Q-PCR reports. The Chk1 protein contents were significantly less in mutant type RNAi-allC than that in KAx-3cells; the Cdc25 protein contents were higher in RNAi-allC cells. The above mentioned results suggest that ATR-Chk1-Cdc25 signaling pathway involved in the regulation of the G2/M phase in Dictyostelium discoideum.

Key words: ATR-Chk1-Cdc25 signaling pathway, G2/M cell cycle, Q-PCR, Western blot, Dictyostelium discoideum