Fig. 4.

Pyrimidine biosynthesis is suppressed in the presence of CII_low. a Label-free quantitative proteomic analysis of downregulated proteins in SDHB^KO MDAMB231 cells and the percentage of proteins identified per pathway relative to genes with significantly altered expression in SDHB^KO cells. b Scheme of the de novo pyrimidine nucleotide synthesis pathway. c SDS-PAGE following WB analysis of MDA231 sublines for proteins of the de novo pyrimidine pathway. d Densitometric evaluation of the level of the CAD and DHODH proteins by WB. Relative isotopomer amounts (M+1) of CTP, CDP, UTP, and UDP were assessed by LC-MS/MS using [U-¹³C] glucose (e) and [U-¹³C] glutamine (f) as tracers. Data shown are mean values ± SD (n ≥ 3); images are representative of at least three independent experiments. The symbol ** indicates differences with p < 0.05 and ‘ns’ indicates non-significant differences, as assessed by the two-tailed unpaired Student’s t-test