Abstract
Glucocorticoids (Gcs) potently inhibit inflammation, and regulate liver energy metabolism, often acting in a hypoxic environment. We now show hypoxic conditions open a specific GR cistrome, and prevent access of GR to part of the normoxic GR cistrome. Motif analysis identified enrichment of KLF4 binding sites beneath those peaks of GR binding exclusive to normoxia, implicating KLF4 as a pioneer, or co-factor under these conditions. Hypoxia reduced KLF4 expression, however, knockdown of KLF4 did not impair GR recruitment. KLF4 is a known target of microRNAs 103 and 107, both of which are induced by hypoxia. Expression of mimics to either microRNA103, or microRNA107 inhibited GR transactivation of normoxic target genes, thereby replicating the hypoxic effect. Therefore, studies in hypoxia reveal that microRNAs 103 and 107 are potent regulators of GR function. We have now identified a new pathway linking hypoxia through microRNAs 103 and 107 to regulation of GR function.
Highlights
Hypoxia is a condition observed in many diseases, such as inflam mation
Our findings reveal that enrichment of Kruppel-like factor 4 (KLF4) motif under glucocorticoid receptor (GR) peaks in normoxia is lost in hypoxia, but KLF4 knockdown alone did not affect GR function
Anti-GR was from BD Biosciences (Oxford, UK); anti-GR (M-20 and H-300) and rabbit IgG were from Santa Cruz Biotech nology, anti-GR (HPA004248), anti-α-tubulin, hypoxia-mimetic defer oxamine and dexamethasone were from Sigma-Aldrich (Dorset, UK); anti-GR (24050-AP-1) was from Proteintech (Manchester, UK); antiphospho-(Ser211)-GR was from Cell Signalling Technology (MA, USA); anti-H3K27ac was from Millipore; horseradish peroxidase con jugated anti-mouse and anti-rabbit were from GE Healthcare (Buck inghamshire, UK); fluorophore conjugated (Alexaflour 488) anti-mouse was from Invitrogen molecular probes (Paisley, UK); TAT3-luc a kind gift of Dr J Lluihi-Ineguez, University of California, San Franscisco, CA, USA
Summary
The tissue response to hypoxia is dominated by the actions of the hypoxia-inducible factors (Moslehi and Rathmell, 2020). These transcription factors are stabilized at the protein level under conditions of low oxygen tension, and they direct an integrated response, with many down-stream genes showing changes in expression, and im pacts on the expression of non-coding RNAs, such as the microRNAs 103 and 107 (Kulshreshtha et al, 2007). Under hypoxic conditions HIF-1α is stabilized and translocates to the nucleus to exert its transcriptional activity. It would be very useful to un derstand why inflammatory diseases frequently require high-dose, high potency glucocorticoid treatment to respond (Yang et al, 2012). One possible factor at sites of active inflammation is reduced oxygen tension
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
