Fig. 3: FBXO7 mediates PRMT1 ubiquitination at lysine 37 in HCC cells.

a Schematic of the workflow for identifying the ubiquitination sites of PRMT1 by mass spectrometry analysis. b Four potential lysine ubiquitination sites (K37, K82, K202, K325) in PRMT1 identified by mass spectrometry analysis. c GFP-PRMT1 (WT or indicated KR mutants) was co-expressed with HA-Ub in FBXO7 KD Huh7 cells rescued with or without FLAG-FBXO7. After MG132 (25 μM, 6 h) treatment, IP was performed with GFP antibody, followed by immunoblotting with indicated antibodies. The immunoblotting experiments were repeated three times with similar results. d FLAG-FBXO7 was co-expressed with GFP-PRMT1 WT or K37R in Huh7 and PLC/PRF/5 cells, followed by immunoblotting with indicated antibodies. The immunoblotting experiments were repeated three times with similar results. e FBXO7 KD cells were transfected with GFP-PRMT1 WT or K37R plasmid, and treated with or without cycloheximide (CHX, 50 μg/mL) for the indicated time. Immunoblotting analysis of GFP-PRMT1 and FBXO7 was performed. Quantitation of GFP-PRMT1 protein level based on band intensity was shown (bottom). Data are presented as the mean ± SD (n  =  3 independent experiments with similar results). Statistical analysis was performed using the two-way ANOVA with Bonferroni correction. f Mass spectrometry identification of K37 ubiquitination of PRMT1. All immunoblotting experiments were repeated three times with similar results. Source data are provided as a Source Data file.