Double-stranded RNA formation leads to preferential nuclear export and gene expression

mRNAs are transcribed and processed in the nucleus before they are exported into the cytoplasm for translation. Export is mediated by the export receptor heterodimer Mex67-Mtr2 in yeast (TAP-p10 in humans). Interestingly, also long non-coding RNAs (lncRNAs) leave the nucleus and so-called XUTs (Xrn1 sensitive unstable transcripts) accumulate in the cytoplasm of the degradation defective xrn1∆ mutant. Curiously, it is currently unclear why so many lncRNAs travel into the cytoplasm. Here we show that such ncRNAs accelerate mRNA export by annealing with their sense counterparts through the helicase Dbp2. These double stranded (ds) RNAs dominate export, because Mex67 has a higher affinity to dsRNAs and more molecules bind. Cells benefit from this mechanism as it quickly regulates gene expression, which is particularly important upon expression program changes. Consequently, prevention of the dsRNA formation or destroying dsRNAs is lethal to cells. This mechanism could explain the general cellular occurrence of antisense RNAs. Cytoplasmic fractionation and RNA extraction.