Journal: Acta Pharmaceutica Sinica. B
Article Title: A novel small molecule inhibitor targeting KHSRP methylation suppresses colon cancer progression
doi: 10.1016/j.apsb.2026.06.031
Figure Lengend Snippet: DIQ01 inhibits PRMT5-mediated methylation of KHSRP. (A) Schematic representation of KHSRP domain architecture across multiple species, highlighting conserved arginine residues (3R: R411, R413, R415; and R442) and the four truncation mutants used for interaction mapping. (B) Representative mass spectra confirming arginine methylation sites on KHSRP. (C) Detection of monomethylarginine (MMA) levels in endogenous KHSRP (HCT116) and exogenously expressed FLAG-tagged KHSRP (HEK293T) following DIQ01 treatment. KHSRP was immunoprecipitated using anti-KHSRP or anti-FLAG antibodies prior to Western blot analysis of MMA. (D) Volcano plot of proteins identified as KHSRP interactors by IP–MS in HCT116 cells. (E) HCT116 and HEK293T cells were co-transfected with FLAG-tagged KHSRP and either HA-tagged PRMT4, PRMT5, or both, with empty vector (EV) as control. KHSRP was immunoprecipitated using anti-FLAG antibody, and monomethylarginine (MMA) levels were detected by Western blot to evaluate PRMT4/5-mediated methylation of KHSRP. (F) Detection of MMA levels in endogenous KHSRP (HCT116) and exogenously expressed FLAG-tagged KHSRP (HEK293T) following treatment with PRMT inhibitors, including a PRMT4-specific inhibitor (EZM2302), a PRMT5-specific inhibitor (GSK591), or their combination. DMSO served as a vehicle control. (G) DIQ01 directly blocked PRMT5-mediated methylation of KHSRP in vitro . Top: DIQ01 concentration series (0–10 μmol/L; “–” no PRMT5, “0” vehicle with PRMT5). Bottom: time course with 2 μmol/L DIQ01 for 2–8 h (“+” DIQ01, “–” vehicle). MMA levels were detected by anti-MMA blot; total KHSRP and PRMT5 served as controls. Data represent ≥3 independent repeats. (H) HCT116 cells and HEK293T (co-expressing FLAG-tagged KHSRP and HA-tagged PRMT5) cells were treated with increasing concentrations of DIQ01. Co-immunoprecipitation was performed using anti-KHSRP antibody (HCT116) or anti-FLAG antibody (HEK293T), followed by immunoblotting for MMA, PRMT5, KHSRP, and FLAG. (I) FLAG-tagged KHSRP mutants carrying single arginine-to-lysine substitutions (R411K, R413K, R415K, or R442K), as well as the combined 3RK mutant, were expressed in HCT116 and HEK293T cells. Immunoprecipitation was performed using anti-FLAG antibody, followed by Western blot analysis of MMA levels. (J) HEK293T cells expressing the same KHSRP mutants (R411K, R413K, R415K, R442K, or 3RK) were treated with or without DIQ01 (500 nmol/L). MMA levels were evaluated by Western blot following FLAG-based immunoprecipitation. (K–M) Functional assays evaluating DNA damage and cell proliferation in HCT116 cells with stable KHSRP knockdown reconstituted with EV, KHSRP WT or KHSRP 3RK . (K) Colony formation assay: cells were cultured for five days, stained with SRB, and relative colony numbers were quantified (mean ± SD, n = 3; ∗∗∗ P < 0.001). (L) Western blot analysis of γ -H2AX expression and (M) alkaline comet assay were performed after 48 h to assess DNA damage, scale bar = 5 μm.
Article Snippet: KHSRP antibody for Western blotting and immunoprecipitation (ABclonal, Cat. No. A9075, Wuhan, China), pan-mono-methyl arginine antibody for Western blotting (ABclonal, Cat. No. A17984), and PRMT4 antibody for Western blotting (ABclonal, Cat. No. A21106) were obtained from ABclonal.
Techniques: Methylation, Immunoprecipitation, Western Blot, Protein-Protein interactions, Transfection, Plasmid Preparation, Control, In Vitro, Concentration Assay, Expressing, Mutagenesis, Functional Assay, Knockdown, Colony Assay, Cell Culture, Staining, Alkaline Single Cell Gel Electrophoresis