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. Author manuscript; available in PMC: 2014 Mar 7.
Published in final edited form as: Mol Cell. 2013 Jan 11;49(5):843–857. doi: 10.1016/j.molcel.2012.12.006

Figure 4. Brd4-Regulated p21 Gene Expression Is p53-Dependent.

Figure 4

(A) Knockdown of Brd4 in 293 by two separate siRNAs reduces Brd4 protein (bottom) and RNA derived from p21 but not RPL13A (bar graph).

(B) Brd4 co-occupies with p53 at -2.3 kb of p21 gene in 293 detected by ChIP with primer pairs as indicated. Two known p53-binding sites (p53BS) are marked.

(C and D) Occupancy of Brd4 and p53 at p21 -2.3 kb in 293 is reduced upon knockdown of Brd4 (C) or p53 (D). Reduced p53 protein level in p53 knockdown is shown.

(E and F) Co-occupancy of p53 and Brd4 at p21 -2.3 kb detectable in p53 +/+ but not p53 -/-HCT116 cells (E) is further enhanced upon Dox (0.5 μM, 6 hr) treatment (F).

(G) Dox-induced p21 RNA level seen in HCT116 p53 +/+, not p53 -/-, cells diminished upon Brd4 knockdown. Error bars, SD (n=2-3) in (A-G).