A versatile interaction platform on the Mex67-Mtr2 receptor creates an overlap between mRNA and ribosome export

The transport receptor Mex67-Mtr2 functions in mRNA export, and also by a loop-confined surface on the heterodimer binds to and exports pre-60S particles. We show that Mex67-Mtr2 through the same surface that recruits pre-60S particles interacts with the Nup84 complex, a structural module of the nuclear pore complex devoid of Phe-Gly domains. In vitro, pre-60S particles and the Nup84 complex compete for an overlapping binding site on the loop-extended Mex67-Mtr2 surface. Chemical crosslinking identified Nup85 as the subunit in the Nup84 complex that directly binds to the Mex67 loop. Genetic studies revealed that this interaction is crucial for mRNA export. Notably, pre-60S subunit export impaired by mutating Mtr2 or the 60S adaptor Nmd3 could be partially restored by second-site mutation in Nup85 that caused dissociation of Mex67-Mtr2 from the Nup84 complex. Thus, the Mex67-Mtr2 export receptor employs a versatile binding platform on its surface that could create a crosstalk between mRNA and ribosome export pathways.