Transforming growth factor β1 alters the 3′-UTR of mRNA to promote lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic disease characterized by the pathological remodeling of air sacs as a result of excessive accumulation of extracellular matrix (ECM) proteins, but the mechanism governing the robust protein expression is poorly understood. Our recent findings demonstrate that alternative polyadenylation (APA) caused by NUDT21 reduction is important for the increased expression of fibrotic mediators and ECM proteins in lung fibroblasts by shortening the 3?-untranslated regions (3?-UTRs) of mRNAs and stabilizing their transcripts, therefore activating pathological signaling pathways. Despite the importance of NUDT21 reduction in the regulation of fibrosis, the underlying mechanisms for the depletion are unknown. We demonstrate here that NUDT21 is depleted by TGF?1. We found that miR203, which is increased in IPF, was induced by TGF?1 to target the NUDT21 3?-UTR, thus depleting NUDT21 in human and mouse lung fibroblasts. TGF?1-mediated NUDT21 reduction was attenuated by the miR203 inhibitor antagomiR203 in fibroblasts. TGF?1 transgenic mice revealed that TGF?1 down-regulates NUDT21 in fibroblasts in vivo. Furthermore, TGF?1 promoted differential APA of fibrotic genes, including FGF14, RICTOR, TMOD2, and UCP5, in association with increased protein expression. This unique differential APA signature was also observed in IPF fibroblasts. Altogether, our results identified TGF?1 as an APA regulator through NUDT21 depletion amplifying pulmonary fibrosis.