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Biochim Biophys Acta Gene Regul Mech. 2019 Jan;1862(1):71-83. doi: 10.1016/j.bbagrm.2018.11.003. Epub 2018 Nov 20.

Deletion of an intronic HIF-2α binding site suppresses hypoxia-induced WT1 expression.

Author information

1
Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany.
2
Klinik für Neonatologie, Charité-Universitätsmedizin Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
3
Institut für Vegetative Physiologie, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany. Electronic address: holger.scholz@charite.de.

Abstract

Hypoxia-inducible factors (HIFs) play a key role in the adaptation to low oxygen by interacting with hypoxia response elements (HREs) in the genome. Cellular levels of the HIF-2α transcription factor subunit influence the histopathology and clinical outcome of neuroblastoma, a malignant childhood tumor of the sympathetic ganglia. Expression of the Wilms tumor gene, WT1, marks a group of high-risk neuroblastoma. Here, we identify WT1 as a downstream target of HIF-2α in Kelly neuroblastoma cells. In chromatin immunoprecipitation assays, HIF-2α bound to a HRE in intron 3 of the WT1 gene, but not to another predicted HIF binding site (HBS) in the first intron. The identified element conferred oxygen sensitivity to otherwise hypoxia-resistant WT1 and SV40 promoter constructs. Deletion of the HBS in the intronic HRE by genome editing abolished WT1 expression in hypoxic neuroblastoma cells. Physical interaction between the HRE and the WT1 promoter in normoxic and hypoxic Kelly cells was shown by chromosome conformation capture assays. These findings demonstrate that binding of HIF-2α to an oxygen-sensitive enhancer in intron 3 stimulates transcription of the WT1 gene in neuroblastoma cells by hypoxia-independent chromatin looping. This novel regulatory mechanism may have implications for the biology and prognosis of neuroblastoma.

KEYWORDS:

Chromosome conformation capture; Gene expression; Hypoxia; Neuroblastoma; Transcription factor; Tumor suppressor

PMID:
30468780
DOI:
10.1016/j.bbagrm.2018.11.003
[Indexed for MEDLINE]

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