HDAC4 Protein Regulates HIF1α Protein Lysine Acetylation and Cancer Cell Response to Hypoxia

Hypoxia-inducible factor 1 α (HIF1α) is an essential part of the HIF-1 transcriptional complex that regulates angiogenesis, cellular metabolism, and cancer development. In von Hippel-Lindau (VHL)-null kidney cancercell lines, we reported previously that HIF1α proteins can be acetylated and inhibited by histone deacetylase ( HDAC) inhibitorsor specific siRNA against HDAC4. To investigate the mechanism and biological consequence of the inhibition, we have generated stable HDAC4knockdown via shRNA in VHL-positive normal and cancer cell lines. We report that HDAC4regulates HIF1α protein acetylation and stability. Specifically, the HIF1α protein acetylation can be increased by HDAC4shRNA and decreased by HDAC4overexpression. HDAC4shRNA inhibits HIF1α protein stability. In contrast, HDAC1or HDAC3shRNA has no such inhibitory effect. Mutations of the first five lysine residues (lysine 10, 11, 12, 19, and 21) to arginine within the HIF1α N terminus reduce protein acetylation but render the mutant HIF1α protein resistant to HDAC4and HDACi-mediated inhibition. Functionally, in VHL-positive cancer cell lines, stable inhibition of HDAC4decreases both the HIF-1 transcriptional activity and a subset of HIF-1 hypoxia target gene expression. On the cellular level, HDAC4inhibition reduces the hypoxia-related increase of glycolysis and resistance to docetaxel chemotherapy. Taken together, the novel biological relationship between HDAC4and HIF1α presented here suggests a potential role for the deacetylase enzyme in regulating HIF-1 cancer cell response to hypoxia and presents a more specific molecular target of inhibition.