First published January 14, 2020 - More info
Alternative polyadenylation (APA) is a widespread and important mechanism in regulation of gene expression. Dysregulation of the 3’ UTR cleavage and polyadenylation represents a common characteristic among many disease states including lung fibrosis. In this study, we investigated the role of mammalian cleavage factor I (CFIm)-mediated APA in regulating the extracellular matrix production in response to mechanical stimuli from stiffened matrix simulating the fibrotic lungs. We found that stiff matrix downregulates expression of CFIm68, CFIm59 and CFIm25 subunits, and promotes APA in favor of the proximal poly(A) site usage in the 3’ UTRs of type I collagen (COL1A1) and fibronectin (FN1) in primary human lung fibroblasts. Knockdown and overexpression of each individual CFIm subunit demonstrated that CFIm68 and CFIm25 are indispensable attributes of stiff matrix-induced APA and overproduction of COL1A1, whereas CFIm does not appear to mediate stiffness-regulated FN1 APA. Furthermore, expression of the CFIm subunits is associated with matrix stiffness in vivo in a bleomycin-induced mouse model of pulmonary fibrosis. These data suggest that stiff matrix instigates type I collagen biogenesis by selectively targeting mRNA transcripts for 3’ UTR shortening. The current study uncovered a potential mechanism for regulation of the CFIm complex by mechanical cues under fibrotic conditions.