Ribosomal proteins are assembled together with the different rRNAs in the nucleolus following a complex process of maturation to give rise to the ribosomal subunits 40S and 60S. Although is known that preribosomal subunits are exported by separate routes that involve CRM1 and RanGTP, nowadays the exact mechanism followed by 40S preribosomal subunits to leave the nucleus remains unclear [163] . However, 60S preribosomal subunit relies on Nmd3 adaptor, which mediates the interaction with CRM1 [179, 180] . The release of the 60S preribosomal subunit requires two GTPase steps: (i) the hydrolysis of the Ran-associated GTP induces the liberation of CRM1; and (ii) the hydrolysis of GTP mediated by the cytoplasmic GTPase Lsg1, which induces the release of Nmd3 [181] .