Design and functional validation of a mutant variant of the lncRNA HOTAIR to counteract Snail function in Epithelial-to-Mesenchymal Transition.

HOTAIR is a lncRNA overexpressed in several epithelial cancers and strongly correlated with invasion. This lncRNA was proven a pivotal element of the epithelial-mesenchymal transition (EMT), a trans-differentiation process triggering metastasis. Snail, master inducer of EMT, requires HOTAIR to recruit EZH2 on specific epithelial target genes (i.e., HNF4α, E-cadherin and HNF1α) and cause their repression. Here we designed a HOTAIR deletion mutant form, named HOTAIR-sbid, including the putative Snail-binding domain but depleted of the EZH2 binding domain. HOTAIR-sbid acted as a dominant negative of the endogenous HOTAIR. In both murine and human tumor cells, HOTAIR-sbid impaired the ability of HOTAIR to bind Snail and, in turn, trigger H3K27me3/EZH2-mediated repression of Snail epithelial target genes. Notably, HOTAIR-sbid expression was proven to reduce cellular motility, invasiveness, anchorage-independent growth, and responsiveness to TGFs-induced EMT. These data provide evidence on a lncRNA-based strategy to effectively impair the function of a master EMT-transcriptional factor.