A molecular switch orchestrates the nuclear export of human messenger RNA

The nuclear export of messenger RNA (mRNA) is a key step in eukaryotic gene expression (Köhler and Hurt, 2007). Despite recent insights into the packaging of newly transcribed mRNAs into ribonucleoprotein complexes (mRNPs) (Pacheco-Fiallos et al., 2023; Bonneau et al., 2023), the subsequent events that govern mRNA export are poorly understood. Here, we elucidate the molecular basis of human mRNA export licensing, which involves the remodeling of mRNP-bound transcription-export complexes (TREX), the formation of export-competent mRNPs, the docking of mRNPs at the nuclear pore complex (NPC), and the release of mRNPs at the NPC to initiate export. Our biochemical and structural data uncover the ATPase DDX39/UAP56 as a central molecular switch that directs mRNPs through the TREX and the NPC-anchored TREX-2 complexes using its ATPase and mRNA-binding cycle. Collectively, these findings establish a mechanistic framework for a general and conserved mRNA export pathway.