Nuclear import of an intact preassembled proteasome particle

• DOI: 10.1091/mbc.e10-07-0595
• Publication Date: 2011-02-03T05:14:26Z
• Authors: Anca F. Savulescu; Hagai Shorer; Oded Kleifeld; Ilana Cohen; Rita Gruber; Michael H. Glickman; Amnon Harel
• Keywords: Nucleoplasm; Nuclear pore; Nuclear lamina; Nucleoporin; Nuclear export signal

The 26S proteasome is a conserved 2.5 MDa protein degradation machine that localizes to different cellular compartments, including the nucleus. Little known about specific targeting mechanisms of proteasomes in eukaryotic cells. We used cell-free nuclear reconstitution system test for and import distinct species. Three types stable, proteolytically active particles were purified from Xenopus egg cytosol. Two these, holoenzyme 20S core particle, targeted periphery but did not reach nucleoplasm. This depends on presence mature pore complexes (NPCs) envelope. A third, novel form, designated here as 20S+, was actively imported through NPCs. 20S+ particle resembles recently described structural intermediates other systems. Nuclear this requires functional NPCs, it directly regulated by Ran GTPase cycle. mere associated “+” factors sufficient reconstitute confer onto isolated ability be imported. Stable found unfertilized eggs may provide means quick mobilization existing into newly formed compartments during early development.