FIG. 9.

p73 recruits Zac1 together with PCAF and p300 to the p21^Cip1 promoter. (A) Scheme of the p21^Cip1 promoter. The locations of the upstream (UPS) and downstream (DS) promoter regions and the distal (BS1) and proximal (BS2) DNA-binding sites of p73 are shown. (B) ChIP analysis of p73 or Zac1 occupancy at the p21^Cip1 promoter. ChIP assays were conducted in the presence (+Lif) or absence (-Lif) of Lif for 3 days. In the presence of Lif, p73 and Zac1 mainly colocalize to the distal p73 DNA-binding site and are selectively accumulated at this site upon Lif withdrawal. (C) Sequential ChIP analysis of p73 or Zac1 occupancy at the p21^Cip1 promoter indicates that p73 and Zac1 co-occupy the distal p73 DNA-binding site. (D) ChIP for p73 or Zac1 occupancy at the p21^Cip1 promoter following p73 or control siRNA transfections on day 1 of Lif withdrawal. The cells were harvested for the ChIP experiments 2 days later. The values for the control siRNA treatments were set to 100%. The knockdown of p73 strongly reduces the binding of p73 and Zac1 to the distal p73 DNA-binding site. (E to F) ChIP analysis of (E) PCAF or (F) p300 occupancy at the p21^Cip1 promoter. (B to F) P values were calculated by Student's t test for differences with versus without Lif or control versus factor-specific siRNA. *, P < 0.05; **, P < 0.01.