Structural investigation of the NTF2‐like RNA binding domain of C. elegans NXF‐2 in complex with NXT‐1

Abstract

The first step governing mRNA export and metabolism is the sorting of processed transcripts into specific nuclear export pathways. mRNA nuclear export and regulation is orchestrated by the nuclear export factor (NXF) family. The NXF NTF2‐like domain, required for nuclear export, is an important interaction domain that heterodimerizes with NXT1 (also an NTF2‐like protein) and directly binds nuclear pore FG repeats. We found that the NTF2‐like domain of both C. elegans NXF‐2 (CeNXF‐2) and human NXF1 possesses novel high affinity RNA binding activity. Here, we present the 1.8Å crystal structure of the NTF2‐like domain from CeNXF‐2 bound to its protein partner CeNXT‐1. Structural analysis reveals a putative RNA binding site on CeNXF2, not present on CeNXT1, and also shows a clear FG binding pocket suggesting possible nuclear pore binding and shuttling activity. Additionally, both CeNXF‐2 and CeNXT‐1 appear to be fairly flexible/dynamic outside of their dimer interface. The presence of additional binding pockets in this structure suggests that the list of functions ascribed to the NTF2 fold is not yet complete. Furthermore, RNA binding activity of the NTF2‐like domain implies that its role in NXF mediated RNA export/regulation is not completely understood. Structural characterization of the putative RNA binding site and of the additional binding pockets is currently underway.