MicroRNAs (miRNAs) are 17-22 nucleotide, non-coding, single stranded RNA molecules
that play a key role in post-transcriptional gene regulation. Hypoxia is a reduction in the normal level
of tissue oxygen (O2) tension, and is a feature of chronic vascular disease, pulmonary disease and
many cancers. Tissue hypoxia can have widespread effects on cellular functions, as O2 availability is
critical for many cellular processes. Cells respond to changes in O2 tension through multiple molecular
and cellular mechanisms, including changes in gene expression through transcriptional and translational
mechanisms. The transcription factor, hypoxia inducible factor-1, plays a dominant role in transcriptional
gene regulation in hypoxia. Several hypoxically induced miRNAs have been shown to play
important roles in the hypoxic adaptation of cancer cells. Global repression of enzymes critical for
miRNA biogenesis seems to be a widespread phenomenon with several different mechanisms operating.
This review describes the effects of hypoxia on specific miRNAs and more global effects on
miRNA biogenesis, demonstrating that hypoxia is an important regulator of miRNA biogenesis and
Keywords: Biogenesis, DICER, DROSHA, HIF, hypoxia, microRNA.
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