Figure 5

SMYD3 stabilizes and activates HIF1α independent of its methyltransferase activity. A and B, qPCR analysis of PGK1 (A) and PDK1 (B) mRNA in HEK293T cells transfected with expression plasmids encoding wildtype SMYD3 or its enzymatically dead mutant SMYD3-F183A (HA empty vector [EV] was used as a control) under normoxia (21% O₂) or hypoxia (1% O₂) for 24 h. Data show mean ± SD; Student’s two-tailed t test. ns, not significant, ∗p < 0.05, ∗∗p < 0.01. Data from three independent experiments. C, co-immunoprecipitation of HA-SMYD3-F183A with Myc-HIF1α. HEK293T cells were cotransfected with indicated plasmids for 24 h. Anti-HA antibody-conjugated agarose beads were used for immunoprecipitation, and the interaction was detected by immunoblotting with the indicated antibodies. D and E, immunoblotting of exogenous Myc-HIF1α expression in HEK293T (D) or H1299 (E) cells transfected with expression plasmids encoding wildtype SMYD3 or its enzymatically dead mutant SMYD3-F183A (HA empty vector [-] was used as a control). The relative intensities of HIF1α were determined by normalizing the intensities of HIF1α to the intensities of GAPDH. Data show mean ± SD; Student’s two-tailed t test. ns, not significant, ∗∗p < 0.01, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001. Data from three independent experiments. qPCR, quantitative RT–PCR; HIF, hypoxia-inducible factor.