Fig. 5: UBA1^ms in MDS-SF3B1 patients confers sensitivity to UBA1 inhibition.

A Experimental strategy to assess the effect of UBA1 inhibition by TAK-243 on the viability of HSPCs derived from SF3B1^WT and SF3B1^K700E iPSCs. B IC₅₀ of TAK-243 in SF3B1^WT and SF3B1^K700E iPSC-derived HSPCs treated with TAK-243 or DMSO for 24 h (n = 3), quantified from dose-response curves in supplementary Fig. 7B. Mean ± SEM. Unpaired t-test. C Sashimi plots of the mis-spliced region in UBA1 from total RNA sequencing of SF3B1^K700E iPSC-derived erythroblasts and primary CD34⁺ BM MNCs from the original MDS-SF3B1 patient. D Sashimi plots of read counts of the mis-spliced region in UBA1 in MDS-RS patients and healthy donors, grouped by splicing factor mutation status, from our previously published data [36] (n^SF3B1 = 83, n^SRSF2 = 15, n^U2AF1 = 4, n^SFWT = 22, n^NBM = 16). E Violin plots of UBA1 intron 5 mis-splicing PSI from total RNA sequencing of CD34⁺ BM MNCs from the same patient cohort, organized by splicing factor mutation. F qPCR analysis of UBA1^ms relative to 18S in CD34⁺ (filled circles) or CD34^- (empty circles) cells from primary BM MNCs of healthy donors (NBM; n = 6) and SF3B1-mutated MDS patients (SF3B1^mt; n = 7). Mean ± SEM relative expression. Unpaired t-test G Experimental strategy to assess the effect of UBA1 inhibition on colony growth and composition in CD34⁺-enriched BM MNCs from MDS-SF3B1 patients and healthy controls. H Effect of UBA1 inhibition on CFU counts relative to DMSO and I frequency of SF3B1^WT and SF3B1^mt colonies relative to total CFU counts from MDS patient (n = 3) or healthy control (n = 2) cells treated with 32 nM TAK-243 or DMSO for 14 days. Numbers within brackets indicate colonies assessed by ddPCR. Mean ± SEM. Unpaired t-test. *, P ≤ 0.05; ***, P ≤ 0.001; ns not significant. SF3B1^mt SF3B1-mutated, MDS-RS MDS with ring sideroblasts, NBM normal bone marrow from healthy donors.