Fig 2: Sm and CHTOP methylarginine mediates PRMT-dependent RI.(a) Comparison of ?? for RI following SNRPB knockdown (kd), GSK591 treatment, MS023 treatment, and CHTOPkd where ??=? (Treatment)–? (Control). (b, c) Comparison of ?? z-score for common RI between SNRPBkd and CHTOPkd with either GSK591 (b) or MS023 (c) treatment. (d) Spearman rank correlation of ?? for common RI between SNRPBkd and CHTOPkd with either GSK591 or MS023 treatment. (e) Schematic of Sm expression constructs where lollipops represent individual methylarginines. (f) RT-qPCR of RI following transduction with Sm R-to-A or R-to-K mutants relative to wild-type (WT). Data are represented as mean ± SD. Significance determined using Student’s t-test; *<0.05, ***<0.001, ****<0.0001. (g) Schematic of CHTOP expression construct as in panel (e). (h) RT-qPCR of RI following transduction with CHTOP R-to-A or R-to-K mutants relative to WT. Data are represented as mean ± SD. Significance determined using Student’s t-test; ***<0.001, ****<0.0001, ns=not significant.

Fig 3: PRMT inhibition promotes aberrant binding of RNA processing factors to chromatin-associated poly(A) RNA.(a) Overview of chromatin-associated poly(A)-RNA LC-MS/MS experiment. (b, c) Dot plot of proteins bound to chromatin (b) or chromatin-associated poly(A) RNA (c) relative to DMSO. Circle size is proportional to -log2(p). Colored values denote factors with ontology pertaining to RNA splicing, transport, or degradation. The names of the top 15 significant proteins are labeled. Significance determined using a heteroscedastic t-test. (d, e) Venn diagram comparing proteins containing methylarginine (Maron et al., 2021) and those that were differentially enriched in the chromatin (d) or chromatin-associated poly(A) (e) fractions following PRMT inhibition. (f) Western blot of chromatin following 2-day treatment with DMSO, GSK591, or MS023. See Figure 4—source data 1. (g) Immunoprecipitation and analysis of CHTOP and SNRPB methylarginine following treatment with DMSO, GSK591, or MS023 for 2 days. See Figure 4—source data 2. Figure 4—source data 1.Western blot data for Figure 4f. Figure 4—source data 2.Western blot data for Figure 4g.