CHK1 activation is compromised in the absence of SHP2.

<p>(<b>A</b>) HU-induced CHK1 activation is dependent on SHP2. HeLa cells were transfected with control, siSHP2, or siCHK1. The cells were treated with HU and harvested at different time points. Lysates were prepared and analyzed with immunoblotting. (<b>B</b>) CIS-induced CHK1 activation is dependent on SHP2. Control- or SHP2 siRNA-transfected HeLa cells were treated with CIS and harvested at different time points. Lysates were prepared and analyzed with immunoblotting.