UC Davis

Eukaryotic gene expression is compartmentalized with transcription of genetic information from DNA into messenger RNA (mRNA) occurring in the nucleus and translation of these messages into proteins occurring in the cytoplasm. These cellular processes are physically separated by the nuclear envelope, a double membrane system that prevents exchange of macromolecules between nuclear and cytoplasmic compartments. RNA and proteins are not able to passively diffuse across this barrier but rather require transport receptors to facilitate docking and transit in and out of the nucleus through Nuclear Pore Complexes (NPCs). A GTP driven process that requires the small Ras like GTPase Ran to regulate nucleocytoplasmic shuttling of cargo is traditionally thought to regulate non-coding RNA (ncRNA) localization. Meanwhile mRNA export is regulated by the heterodimeric transport receptor Mex67-Mtr2 (Tap-p15/NXF1-NXT1 in humans) and ATP via the activity of the DEAD box Protein 5 (Dbp5 in yeast, DDX19 in humans), which is not directly dependent on Ran function. The work presented here describes how Dbp5 also regulates ncRNA export, revealing a novel ATP driven ncRNA export pathway and broader functions of mRNA export factors Dbp5 and Mex67 as general RNA export adapters.