Fig. 4: SMOX plays a crucial role in maintaining eIF5A hypusination and protein synthesis in OIS.

a Schematic for ¹³C₆-Arginine tracing into the polyamine synthesis pathway. Black circles represent ¹²C atoms, while red circles represent ¹³C atoms. b Tracing analysis from ¹³C₆-Arginine OIS cells transfected with siRNAs targeting SAT1 or SMOX. Data represent mean ± SD from biologically independent experiments (n = 3). p-values were calculated using a two-tailed unpaired t test. NS, not significant; *P  <  0.05; **P  <  0.01; ***P  <  0.001. c Immunoblot assay of hypusinated eIF5A (Hyp-eIF5A), total eIF5A, and SMOX in OIS cells transfected with siRNAs against SMOX and treated with 10 μM spermidine (Spd). d Quantification of OP-Puro incorporation in OIS BJ-Ras-ER cells transfected with either siRNA control or SMOX siRNAs. Cells were treated with 10 μM spermidine. Data represent mean ± SD from biologically independent experiments (n = 3). p-values were calculated using a two-tailed unpaired t test. NS is not significant; *P  <  0.05; **P  <  0.01. e Senescence-associated beta-galactosidase (SA-β-gal) assay in OIS BJ-Ras-ER cells transfected with siRNAs against SMOX. Data represent mean ± SD from biologically independent experiments (n = 3). p-values were calculated using a two-tailed unpaired t test. NS is not significant. f Quantification of BrdU incorporation in OIS BJ-Ras-ER cells transfected with siRNAs against SMOX. Data represent mean ± SD from biologically independent experiments (n = 3). p-values were calculated using a two-tailed unpaired t test. NS is not significant. Source data, including exact p-values, are provided as Source Data files.