IκBα (C-21, sc-371), p65 (C-20, sc-372), and phospho-threonine (H-2, sc-5267) antibodies were from Santa Cruz Biotechnology; β-actin (AC-15, A5441), Flag (M2, F3165), HA (HA-7, H3663), importin-α (IM-75, I1784), and importin-β (31H4, I2534) antibodies were from Sigma; PARP (C2-10, 556362), IKKα (B78-1, 556532), and IKKβ (24, 611254) antibodies were from BD Pharmingen; CK2α (31, 611610) and Hsp90 (68, 610418) antibodies were from BD Transduction Laboratories; phospho-IκBα (5A5, 9246S) and phospho-IKKα/β (16A6, 2697S) antibodies were from Cell Signaling Technology; phospho-serine (AB1603) and phospho-tyrosine (4G10, 05-777) antibodies were from Millipore. The rabbit polyclonal RPS3 antiserum was as described previously6.