Nuclear export of 60S ribosomal subunits depends on Xpo1p and requires a nuclear export sequence-containing factor, Nmd3p that associates with the large subunit protein Rpl10p

Nuclear export of ribosomes requires a subset of nucleoporins and the Ran s ystem, but specific transport factors have not been identified. Using a lar ge subunit reporter (Rp125p-eGFP), we have isolated several temperature-sen sitive ribosomal export (rix) mutants. One of these corresponds to the ribo somal protein Rpl10p, which interacts directly with Nmd3p, a conserved and essential protein associated with 60S subunits, We find that thermosensitiv e nmd3 mutants are impaired ill large subunit export. Strikingly, Nmd3p shu ttles between the nucleus and cytoplasm and is exported by the nuclear expo rt receptor Xpo1p. Moreover, we show that export of 60S subunits is Xpo1p d ependent. We conclude that nuclear export of 60S subunits requires the nucl ear export sequence-containing nonribosomal protein Nmd3p, which directly b inds to the large subunit protein Rpl10p.