Inhibition of SPT disrupts nuclear membrane integrity and causes lethality in yeast. (a) Live-cell microscopy of yeast cells expressing Heh1-GFP treated with 5 µM myriocin or 10 µM cerulenin for the indicated times. DIC, differential interference contrast. Scale bar, 5 µm. (b) Quantification of the nuclear phenotype of yeast cells treated with 5 µM myriocin or 10 µM cerulenin (n = 200 cells) at indicated times. (c) Representative images of CFU assay of yeast cells following treatment with 5 µM myriocin or 10 µM cerulenin at 0 or 4 h. Scale bar, 1 cm. (d) Percentage of viable cells quantified by CFU of 200 cells (n = 3). Error bars represent the standard deviation. *P < 1 e-4, one-way ANOVA test. NS, P > 0.05. (e) Growth curves of yeast cells quantified with a Coulter counter at indicated time points. *P < 1 e-5, paired t test. (f) HPLC-MS/MS analysis of LCBs and ceramides in yeast cells treated with 5 µM myriocin or 10 µM cerulenin at indicated times. Columns represent experiments, and rows represent lipid species. Log₂ ratios of the relative lipid levels in comparison with untreated cells are shown. Cer, ceramide; dh, dihydro; DHS, dihydrosphingosine; PHS, phytosphingosine. (g and h) Plots of the total lipid classes as a function of time of the lipidome data presented in Fig. 2 f.CFU, colony-forming unit; HPLC-MS/MS, high-performance liquid chromatography–tandem mass spectrometry.