Coupling of nuclear RNA export and protein import in vertebrate cells.

Nuclear RNA export is a highly dynamic process in which factors that carry the RNAs out of the nucleus must be re-imported. These RNA export factors are bifunctional molecules that recognize specific RNA sequences or structures and interact with shared nuclear proteins, including components of the nuclear pore complex. Inhibition of protein import by inactivation of the GTPase Ran, or its associated activating and recycling factors, blocks RNA export. However a few classes of RNAs escape this inhibition, perhaps because they do not use shuttling export factors or their factors have been stockpiled in the nucleus. Because of its critical role in gene expression, RNA export is a target for control by both cells and viruses.