Figure 6. MARVELD1 represses the recruitment of SMG5 by inhibiting serine phosphorylation of UPF1.
(A) HeLa cells transiently transfected with two independent siRNAs against MARVELD1 or the negative control siRNA and HEK293/MARVELD1 or the control cells HEK293/Vector were analyzed by coimmunoprecipitation using anti-UPF1 or rabbit (r) IgG in the presence of RNase A. The analysis of the intensity of SMG1 and importin β1 immunoprecipitated by anti-UPF1 is displayed as histograms on the right. The coIPs of SMG1 and importin β1 were both normalized to the amount of UPF1 immunoprecipitated by anti-UPF1. (B) Lysates of HeLa cells transiently depleted of MARVELD1 and HEK293/MARVELD1 were transiently transfected with Flag-UPF1 and immunoprecipitated by anti-Flag or mouse (m) IgG. Western blotting was performed using anti-phosphoserine or anti-SMG5. The intensities of phosphoserine level and the SMG5 immunoprecipitated by anti-Flag were normalized to the total Flag-UPF1 and are displayed as histograms on the right. (C) The effects of siRNA-mediated knockdown of MARVELD1 and the overexpression of MARVELD1-V5 were assessed by western blotting. GAPDH was used as an internal control. The average ± S.E. (error bars) is displayed.