Fig. 1: Uridine phosphorylase activity supports growth on uridine or RNA.
From: Salvage of ribose from uridine or RNA supports glycolysis in nutrient-limited conditions
a, Schematic overview of the ORF proliferation screen. b, Volcano plot representation of the screen hits after 21 d of growth in medium containing 25 mM glucose or 25 mM galactose, 0.2 mM uridine and 1 mM sodium pyruvate (n = 2). LFC, log2 (fold change). P values were calculated using a two-sided Student’s t-test. Statistics were not adjusted for multiple comparisons. c, Reaction catalysed by UPP1 and UPP2 proteins. d–f, Cell growth assays of K562 control cells and K562 cells expressing UPP1-FLAG or UPP2-FLAG in pyruvate-free media in the presence of: 25 mM glucose or 25 mM galactose or 0.2 mM uridine (±U; n = 3 replicate wells, P < 1.1 × 10−4 and P < 4.7 × 10−5; d), 10 mM of either glucose, galactose or uridine (n = 3, P < 2.1 × 10−5; e) or 5 mM of the indicated nucleosides (n = 3, P < 2.0 × 10−7; f). Data are shown as the mean ± s.e.m. with two-sided t-test relative to control cells. g, Schematic of RNA highlighting its ribose groups. h, Intracellular abundance of the four nucleoside precursors of RNA in control or UPP1-FLAG-expressing K562 cells grown in sugar-free medium supplemented with 0.5 mg ml−1 purified yeast RNA after 24 h. Data are expressed as fold changes of sugar-free medium (n = 4, P < 1.2 × 10−6) and shown as the mean ± s.e.m. with two-sided t-test relative to control. i, Cell growth assays of control or UPP1-FLAG-expressing K562 cells in sugar-free medium supplemented with 0.5 mg ml−1 of purified yeast RNA (n = 3, P < 2.6 × 10−5). Data are shown as the mean ± s.e.m. with two-sided t-test relative to control cells. All growth assays, metabolomics and screens included 4 mM l-glutamine and 10% dialysed FBS.
