EVIDENCE THAT VAULT RIBONUCLEOPROTEIN-PARTICLES LOCALIZE TO THE NUCLEAR-PORE COMPLEX

Vaults are cytoplasmic ribonucleoprotein organelles that are highly co nserved among diverse eukaryotic species. Their mass (12.9 MDa), diame ter (26-35 nm) and shape (two halves, each with eightfold radial symme try) have recently been determined and are similar to those ascribed t o the central plug (or transporter) of the nuclear pore complex (NPC). The size and eightfold symmetry of the vault particle make it conduci ve to interacting physically in a complementary manner with NPCs. The present study demonstrates that vaults specifically associate with nuc lei by both immunoblotting and immunofluorescence. Immunogold EM confi rmed that vaults associate with the nuclear envelope in tissue section s and with NPCs of isolated nuclei.