The RNA-binding protein HuR regulates microRNA biogenesis via increased drosha expression

Background

The biogenesis of microRNAs (miRNAs) undergoes substantial alterations in response to various stressors. Drosha, a pivotal regulator of miRNA biogenesis, plays a critical role in cellular responses to external stimuli. The RNA-binding protein HuR is upregulated upon cellular stress. However, under severe or prolonged stress conditions, HuR levels may decline, impairing its protective functions.

Methods

To investigate the influence of HuR on miRNA expression, miRNA sequencing was employed to profile expression in IEC-6 intestinal epithelial cells following HuR silencing. Additionally, the effect of HuR overexpression on Drosha expression and activity was assessed. Bioinformatics analyses, biochemical assays, and molecular biology techniques were utilized to elucidate the mechanisms by which HuR interacts with Drosha mRNA, modulating both its translation and transcription.

Results

HuR silencing resulted in a significant downregulation of nearly all miRNAs, with no observed impact on piRNA biogenesis. Conversely, HuR overexpression led to increased Drosha expression, regulated through HuR's direct binding to the 3′-UTR of Drosha mRNA. Moreover, HuR indirectly promoted Drosha transcription by elevating c-Myc levels. In a mouse model of thoracic trauma, diminished HuR expression in the intestinal epithelium correlated with reduced Drosha levels, impairing miRNA biogenesis and enhancing apoptosis.

Conclusions

These findings underscore the essential role of HuR in the regulation of miRNA biogenesis through Drosha, with implications for stress responses and intestinal injury. The HuR-Drosha axis emerges as a promising therapeutic target for modulating miRNA biogenesis.