TFAP2A mediates HIF-1α dependent activation of hypoxia-inducible genes via interaction with Ku70/80 complex in a SUMO-dependent manner

Hypoxia can be established under pathological conditions, such as cancer, due to the imbalance between oxygen supply and consumption. Hypoxia Inducible Transcription Factor HIF-1 mediates the physiological response to hypoxia but also regulates multiple steps of carcinogenesis. Despite its well-defined oxygen-dependent activation, many aspects of HIF-1 transcriptional activity as well as interaction with chromatin remain elusive. We have recently shown that TFAP2A physically interacts with HIF-1 and hypoxia-dependent deSUMOylation of TFAP2A positively affects HIF-1 activity. We now present ChIP-seq analysis showing that TFAP2A resides together with HIF-1α on the promoters of a subset of hypoxia-regulated genes, the mRNA expression of which is downregulated by silencing of TFAP2A. Interestingly, CRISPR-mediated knockdown of TFAP2A expression under hypoxia decreased the occupancy of HIF-1α on these promoters and affected chromatin accessibility. Mechanistically, we reveal that the Ku70/Ku80 protein complex interacts with TFAP2A in a SUMO-dependent manner under hypoxia and participates in HIF-dependent gene expression. Moreover, using stable expression of TFAP2A forms that either lack or constitutively carry a SUMO modification, we could show that SUMOylation affects binding of TFAP2A to chromatin. Overall, our data suggest that TFAP2A is an important co-regulator of the HIF-1-dependent transcriptional response to hypoxia and SUMOylation fine-tunes this regulation. As both TFAP2A and HIF-1 play critical roles in cancer progression, a detailed characterization of their crosstalk could lead to novel therapeutic strategies for targeting and killing cancer cells in hypoxic tumors