Fig. 4: Identification of transcription factors regulating ACE2 expression in response to leucine deprivation.

a CCD841 cells were transfected with control small interfering RNAs (siNC) or small interfering RNAs targeting at human GCN2 (siGCN2). After 12 h, cells were incubated with either control (Con) or leucine-deprived culture medium ((−) LEU) for 48 h. RNA-seq analysis of differentially expressed transcription factors that were increased under leucine starvation ((−) LEU) (fold change > 1.5, p value < 0.05) and decreased by GCN2 knockdown (fold change < 0.7, p value < 0.05). b–e CCD841 cells were transfected with siNC, siMAFB, siMAFF, control plasmids (pCMV-HA), HA-tagged MAFB (HA-MAFB), or HA-tagged MAFF (HA-MAFF) for 48 h. MAFB and MAFF protein expression were measured by western blotting (upper); MAFB, MAFF, and ACE2 mRNA expression was measured by qRT-PCR (bottom). f, g CCD841 cells were transfected with siNC, siMAFB or siMAFF. After 12 h, cells were incubated with either Con or (−) LEU culture medium for 48 h. mRNA expression of MAFB, MAFF, and ACE2 were analyzed by qRT-PCR. Data are expressed as the mean ± SEM (n = 5–6 per group, as indicated by scatter circles). *P < 0.05, **P < 0.01.