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

Activation of the transforming growth factor ß (TGF-ß) signaling leads to established hallmarks of cancer such as the epithelial-to-mesenchymal transition (EMT), initiating cancer dissemination and increasing chemoresistance. TGF-ß 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-ß 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-ß signaling and EMT, as further validated by functional gain or loss assays. Mechanistically, the TGF-ß-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-ß response in tumor cells via SMAD nucleocytoplasmic shuttling. Overall design: Comparative gene expression profiling analysis of RNA-seq data for A549 lung adenocarcinoma cells trasfected with scrambled siRNA in the presence or absebce of TGFß stimulation in comparison to cells transfected with siRNAs against the long noncoding RNA VIM-AS1 in the presence or absence of TGFß stimulation.