J HEK293T cells transfected with HA-tagged ubiquitin and GST-tagged NEMO mutants together with Strep-tagged empty vector or MARCH2 were subjected to pulldown with GST beads, followed by immunoblotting with anti-Lys48 (K48)-linkage specific polyubiquitin (K48-ub), anti-Lys63 (K63)-linkage specific polyubiquitin (K63-ub), or anti-Strep antibody. Whole cell lysates were determined by immunoblotting with the indicated antibodies. 