Figure 2.

Nonlethal cell cycle block induced by Cdc6 deficiency in RPE1 cells requires ATR. (A) Asynchronous RPE1 cells were treated with siLuc or siCdc6 for 60 h; with siLuc or siCdc6 for 48 h and then 2.5 mM caffeine (CAFF) for 12 h; or with siLuc or siCdc6 for 12 h and then with siATR for 48 h, as indicated. Treated cells were harvested and subjected to FACS. Sub-G1 populations were calculated based upon all counts per sample; G1/S/G2/M populations were calculated from non–sub-G1 counts. As mentioned in Figure 1, G1 contains G1 and G1/S cells and G2/M contains late S and G2/M cells. (B) Cells treated as described in A were subjected to immunoblotting analysis with indicated antibodies.