HIF1/2-exerted control over glycolysis but not OxPHOS pathways in human normal and leukemic stem/progenitor cells

Hypoxia inducible factors (HIF)1 and 2 are transcription factors which regulate the homeostatic response to low oxygen conditions. Since data related to the importance of HIF1 and 2 in haematopoietic stem and progenitors is conflicting, we investigated the chromatin binding profiles of HIF1 and HIF2 and linked that to transcriptional networks and the cellular metabolic state. Genome-wide ChIP-seq and transcriptome studies revealed that overlapping HIF1- and HIF2-controlled loci were highly enriched for various processes like including metabolism, particularly those involved in glucose metabolism, but also for chromatin organization, cellular response to stress and G protein-coupled receptor signaling. ChIP-qPCR validation studies confirmed that glycolysis-related genes - but not genes related to the TCA cycle or glutaminolysis - were controlled by both HIF1 and HIF2 in leukemic cell lines and primary AMLs, while in healthy human CD34+ cells these loci were predominantly controlled by HIF1 but not HIF2. However, and in contrast to our initial hypotheses, CRISPR/Cas9-mediated knockout of HIF signaling did not affect growth, internal metabolite concentrations, glucose consumption or lactate production under hypoxia. These data indicate that, while HIFs exert control over glycolysis but not OxPHOS gene expression in human leukemic cells, this is not critically important for their metabolic state. Overall design: ChIP-seq analysis of tagged HIF proteins in K562 cells was performed using illumina high-throughput sequencing