Supplementary Figure 6: rRNA is the major sink of newly synthesized GTP in GBM cells.

a, FACS-based cell cycle analysis of U87MG cells shows <20% of cells are in S-phase. Data are representatives from n=2 independent experiments. b, Acute inhibition of GMPS, a downstream enzyme of IMPDH, by Acivicin leads to depletion of GTP within 4 h, phenocopying the effect of MPA. Data are presented as mean+s.d. n=3 biologically independent samples. Unpaired two-sided Student’s t-test. c, Marginal accumulation of dGTP and uric acid, one of the final catabolites of GTP, in U87MG cell as well as in the cultured media. U87MG cells were labeled with [U-¹³C]glucose for 4 h and polar metabolites were collected and analyzed by CE-MS as in the method. N.D. stands for not detectable. Data are presented as mean+s.d. n=3 biologically independent samples. d, BMH-21 blocks the MPA-dependent depletion of GTP in U87MG and LN229 cells. GTP concentrations were quantified by HPLC in 10 μM MPA (4 h) and 10 μM BMH-21 (5 h including 1 h pretreatment)-treated U87MG and LN229 cells. Data are presented as mean+s.d. n=3 biologically independent samples. One-way ANOVA. e, A detailed schematic diagram of the procedure of SI-MOIRAI.