Figure 3.

P53 Activates Rb1 to Elongate G1 Phase in 2i ESCs

(A) Bar graph showing differential expression of cell cycle and other regulators in serum and 2i cultured WT and P53^−/− ESCs during G1 phase. The expression of Rb1, Rbl2, and Cdkn1a (P21) is decreased in P53^−/− both in serum and 2i ESCs.

(B and C) (B) A total of 2,585 genes are associated with P53 binding sites, 386 of these genes are expressed differentially in 2i P53^−/− compared with 2i WT cells. (C) ChIP-seq and Capture HiC indicate that P53 binds regions that locate or interact with the TSS of Rb1 and Rbl2.

(D) WB showing that the protein level of hyper-phosphorylated RB (ppRB) and hypo-phosphorylated RB (RB) is reduced in P53^−/− FUCCI ESCs (clone 1) in serum and 2i, respectively.

(E) WB showing the protein level of RB throughout the cell cycle in P53^−/− (clone 1) and WT FUCCI ESCs in serum and 2i conditions. At least two independent experiments showed similar results.

(F) Proposed model that displays the role of P53 and Rb1 in ESC cell cycle control.