Figure 8.

Mcl-1 is required for Ser345 Chk1 phosphorylation after DNA damage. (A) HeLa cells were transfected with control (left two lanes) or Mcl-1 siRNA (right two lanes); 48 h after initial transfection, cells were left untreated (lanes 1 and 3) or were treated with etoposide for 1 h (lanes 2 and 4). Total cell proteins were extracted and immunoblotted with anti-Mcl-1, anti-phospho Chk1 (Ser 345), anti-Chk1, anti-Bcl-2, and anti-p85 antibodies. (B) HeLa cells were transfected with control siRNA or Mcl-1–specific siRNA for 48 h, followed by treatment without or with etoposide for 1 h. Cells were stained with PI and analyzed by flow cytometry for DNA content.