SMAD proteins control DROSHA-mediated microRNA maturation
Brandi N Davis1, Aaron C Hilyard, Giorgio Lagna
1Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Nature
|June 13, 2008
Summary
Transforming growth factor beta (TGF-beta) and bone morphogenetic protein (BMP) signaling rapidly increase microRNA-21 (miR-21) levels. This enhances vascular smooth muscle cell contraction by downregulating PDCD4, a negative regulator of contractile genes.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- MicroRNAs (miRNAs) regulate gene expression but the control of their biogenesis is poorly understood.
- Transforming growth factor beta (TGF-beta) and bone morphogenetic protein (BMP) signaling pathways are crucial for vascular development and homeostasis.
- Dysregulated miRNA expression is linked to diseases like cancer and cardiovascular disorders.
Purpose of the Study:
- To investigate the role of microRNAs in TGF-beta and BMP-induced vascular smooth muscle cell phenotype.
- To elucidate the mechanism by which TGF-beta and BMP signaling regulate miRNA biogenesis.
Main Methods:
- Quantitative real-time PCR to measure miRNA and gene expression.
- Western blotting to assess protein levels.
- Immunoprecipitation assays to study protein-RNA interactions.
Main Results:
- TGF-beta and BMP signaling induce vascular smooth muscle cell contraction via miR-21.
- miR-21 directly downregulates PDCD4, a repressor of smooth muscle contractile genes.
- TGF-beta and BMP signaling enhance mature miR-21 production through post-transcriptional processing of pri-miR-21 by the DROSHA complex.
- SMAD proteins and p68/DDX5 are recruited to pri-miR-21, facilitating processing in a SMAD4-independent manner.
Conclusions:
- TGF-beta and BMP signaling regulate vascular smooth muscle cell phenotype through miR-21.
- Ligand-specific SMAD proteins control miRNA biogenesis at a post-transcriptional level.
- This mechanism highlights a SMAD4-independent regulatory pathway in TGF-beta and BMP signaling.
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