The Cajal body protein coilin is a regulator of the miR-210 hypoxamiR and influences MIR210HG alternative splicing.

Hypoxia is a severe stressor to cellular homeostasis. At the cellular level, low oxygen triggers the transcription of a variety of genes supporting cell survival and oxygen homeostasis mediated by transcription factors, such as hypoxia-inducible factors (HIFs). Among many determinants dictating cell responses to hypoxia and HIFs are microRNAs (miRNAs). Cajal bodies (CBs), subnuclear structures involved in ribonucleoprotein biogenesis, have been recently proven to contribute to miRNA processing and biogenesis but have not been studied under hypoxia. Here, we show, for the first time, a hypoxia-dependent increase in CB number in WI-38 primary fibroblasts, which normally have very few CBs. Additionally, the CB marker protein coilin is upregulated in hypoxic WI-38 cells. However, the hypoxic coilin upregulation was not seen in transformed cell lines. Furthermore, we found that coilin is needed for the hypoxic induction of a well-known hypoxia-induced miRNA (hypoxamiR), miR-210, as well as for the hypoxia-induced alternative splicing of the miR-210 host gene, MIR210HG. These findings provide a new link in the physiological understanding of coilin, CBs and miRNA dysregulation in hypoxic pathology.