Hypoxia regulates GR function through multiple mechanisms involving microRNAs 103 and 107

Area of Science:

• Molecular Biology
• Cellular Metabolism
• Endocrinology

Background:

• Glucocorticoids (Gcs) are crucial regulators of inflammation and liver energy metabolism.
• These processes often occur within a hypoxic (low oxygen) cellular environment.
• The precise mechanisms by which hypoxia influences GR function remain incompletely understood.

Purpose of the Study:

• To investigate how hypoxic conditions specifically alter the binding of the glucocorticoid receptor (GR) in liver cells.
• To identify novel regulatory pathways linking hypoxia to GR function.

Main Methods:

• Chromatin immunoprecipitation sequencing (ChIP-seq) to map GR binding sites under normoxic and hypoxic conditions.
• Motif analysis to identify transcription factor binding sites associated with GR.
• MicroRNA mimic transfection and KLF4 knockdown experiments to assess regulatory roles.

Main Results:

• Hypoxia specifically modifies the GR cistrome, creating a unique binding profile.
• KLF4 binding sites are enriched under normoxia but not hypoxia, suggesting a role in normoxic GR regulation.
• Hypoxia induces microRNAs 103 and 107, which inhibit GR activity on normoxic target genes.

Conclusions:

• MicroRNAs 103 and 107 are key regulators of GR function under hypoxic conditions.
• A novel pathway involving hypoxia, microRNAs 103/107, and GR regulation has been identified.
• This pathway offers new insights into the control of liver metabolism and inflammation.