(A) Reporter cell lines with the indicated KO condition were induced to express LBR1600*S11 and transfected with HA-ubiquitin, incubated for 24 h, and subjected to immunoprecipitation and immunoblotting using the indicated antibodies.
(B) FLAG-tagged E3 ligases and HA-ubiquitin were co-transfected into cells expressing LBR1600*S11, followed by immunoprecipitation and immunoblotting as in (A).
(C) The authentic RNF5 locus of the reporter cell line was tagged with HA, and validated by RNF5 depletion using siRNA and immunoblotting with anti-HA.
(D) Endogenous RNF5 interacts with LBR1600*S11. The reporter cell line with RNF5-HA expressed from the authentic locus was treated with or without doxycycline and MG132, followed by immunoprecipitation with anti-HA antibody and immunoblotting with the indicated antibodies. See also Figure S2.