Abstract
The addition of poly(A) tails (polyadenylation) is a key process in the maturation of mRNA. Alternative polyadenylation (APA) has been found to drive tumorigenic properties in cancer that are mediated by depletion of a 25kDa subunit of cleavage factor I (CFIm25). CFIm25 binds directly to RNA and regulates use of poly(A) sites. Based on these observations, we hypothesized that depletion of CFIm25 and APA played a pathogenic role in the development of pulmonary hypertension (PH).
Immunoblots for CFIm25 showed reduced protein expression in pulmonary artery smooth muscle cells (PASMC) from patients with pulmonary arterial hypertension (PAH) and patients with PH secondary to COPD, compared to healthy controls. In addition, immunohistochemistry demonstrated loss of CFIm25 in remodeled vessels of patients with PAH or COPD + PH. These observations were also corroborated in animal models of PH.
A hallmark of APA is 3'UTR shortening that leads to loss of miRNA binding sites allowing transcripts to escape miRNA regulation resulting in heightened translation. CFIm25 siRNA and subsequent RNAseq experiments revealed 3'UTR shortening in key members of the TGF-β and the Wnt pathways that are known to be elevated in PH. Interestingly; hypoxia appeared to down-regulate expression of CFIm25 in PASMC, suggesting a potential mechanism relevant to PH. In conclusion, we have identified a novel mechanism that may regulate expression of several genes associated with PH that could be exploited therapeutically.
- Copyright ©ERS 2015