EGLN3 suppresses cIAP1-mediated IKKγ ubiquitination. (A to I) HEK293T cells were transfected with the indicated plasmids. (C) At 6 h or so posttransfection, cells were treated with PBS or Smac mimetic (100 nM). Cell lysates were applied to in vivo ubiquitination assays as described in Materials and Methods. Cell lysates were analyzed by immunoblotting. IP, immunoprecipitation; IB, immunoblotting; IgH, heavy chain of IgG; mut, mutant; SM, Smac mimetic.