RNA-binding protein 4 (RBM4) is required for ERBB1 protein upregulation during hypoxia. (A) RBM4 transcript levels after targeted knockdown of RBM4 by short hairpin RNA, indicated as shRBM4 (n ≥ 5 per group). (B) RBM4 protein levels after knockdown of RBM4. One representative blot from three independent experiments is shown. (C) ERBB1 protein levels in normoxia (Nx) and hypoxia (Hx); β-ACTIN was used as a loading control. One representative blot from three independent experiments is shown. (D) Densitometry of ERBB1 western blots (n = 4 per group). *P < 0.05, ***P < 0.001; n.s., nonsignificant. Data are presented as the mean ± SD. (A) Unpaired, two-tailed t test. (D) Two-way ANOVA and Bonferroni adjustment for comparisons between Nx and Hx. (A) t = 12.56, df = 9; (D) F_3,12 = 12.32, P < 0.001.