SMAD nucleocytoplasmic shuttling relies on nucleoporin RanBP2 and VIM-AS1 long non-coding RNA during TGF-β signaling

Activation of the transforming growth factor β (TGF-β) signaling leads to established hallmarks of cancer such as the epithelial-to-mesenchymal transition (EMT), initiating cancer dissemination and increasing chemoresistance. TGF-β signal by binding to its type I and II receptors, leading to parallel activation of SMAD proteins, ubiquitin ligases and protein kinases. Here, using a panel of tumor cells we show that TGF-β activation induces the expression of the mammalian nuclear long non-coding RNA (lncRNA) VIM-AS1 (Vimentin antisense RNA 1) variant 2 (v.2) via the formation of a complex among the transcriptional factors GATA6-SMAD-SPI1. Furthermore, transcriptomic analysis indicated VIM-AS1 enhancing TGF-β signaling and EMT, as further validated by functional gain or loss assays. Mechanistically, the TGF-β-induced VIM-AS1 v.2 enhanced SMAD nucleocytoplasmic shuttling by interacting with the N-terminus domain of the nucleoporin RanBP2 (Nup358), whereby acting as a scaffold molecule, facilitates the binding of RanBP2 with SMAD2/3 and its further nuclear import. Finally, VIM-AS1 increases invasion and motility of tumor cells and emerges as a promising therapeutic target to sensitize cancer cells to chemotherapeutic drugs. Hence, we delineated a novel signaling mechanism for VIM-AS1 v.2 facilitating TGF-β response in tumor cells via SMAD nucleocytoplasmic shuttling.