The nuclear export of mRNA represents a critical regulatory node in eukaryotic gene expression. This process is orchestrated by two conserved multi-subunit assemblies: the transcription-and-export complex (TREX) and TREX-2. While TREX facilitates mRNP packaging through multivalent RNA-protein interactions, the precise mechanism by which TREX-2 contributes to mRNA export has remained elusive. Here, we report a functional interaction between UAP56 and TREX-2 and resolve the structures of TREX-2 in both apo and UAP56-bound states. UAP56 engages TREX-2 via its N-terminal region, positioning its RecA domains on the V-shaped surface of the complex. A conserved loop from TREX-2 inserts between the RecA domains of UAP56, stabilizing an open conformation. Biochemical assays demonstrate that TREX-2 significantly stimulates the ATPase activity of UAP56, thereby promoting RNA release. These findings provide structural and mechanistic insights into TREX-2-mediated regulation of mRNA export through UAP56 remodeling. The nuclear export of mRNA is a crucial regulatory step in eukaryotic gene expression. Here, the authors show that TREX-2 interacts with UAP56, enhances its ATPase activity, and promotes mRNA release from UAP56. These findings provide key insights into the mechanisms underlying mRNA export.
Gong et al. (Thu,) studied this question.