PRMT1 cooperates with FLT3-ITD in regulation of AML. (A) Heat map showing the top 30 upregulated and top 30 downregulated genes in THP-1 and MV4-11 lines expressing ShPRMT1 or ShCtrl, based on a fold-change > 1.5 and P < .05. (B) Bar graphs representing the percentage frequency of primary AML specimens with FLT3-ITD vs FLT3 WT and exhibiting PRMT1 high (normalized score ≥ 0.75) or PRMT1 low (normalized score ≤ −0.75) signatures, based on 2 GEO cohorts (GSE14468, GSE10358). *P < .05, **P < .01, Fisher’s exact test. (C) Co-IP of GFP from GFP-tagged PRMT1-transduced 32D cells ectopically expressing FLT3-ITD, FLT3 WT, or mock and then analyzed for FLT3 and GFP by western blotting. (D) Immunostaining for FLT3 (green), membrane (pink), and 4′,6-diamidino-2-phenylindole (DAPI; blue) in CD34⁺CD38⁻ cells from primary AML specimens with or without FLT3-ITD. Scale bar, 5 μm. (E) Co-IP of endogenous FLT3 from MV4-11 cells after IP with FLT3 antibody followed by FLT3 and PRMT1. (F) Representative images of Duolink in situ proximity ligation assay in primary AML CD34⁺CD38^- cells from 2 primary FLT3-ITD⁺ AML specimens. Red spots indicate PRMT1/FLT3 protein interaction (left), DAPI-stained nuclei are blue (center), and merged image is at right. Scale bar, 5 μm. (G) Hemagglutinin (HA)-tagged FLT3 (ITD 18 bp in-frame insertion at E596 within the juxtamembrane domain) fragments (D1-D3) and GFP-tagged PRMT1 were coexpressed in 293T cells, followed by pull-down with an anti-HA antibody and western blot for HA and GFP-PRMT1.