In Schizosaccharomyces pombe, Cut8 is a nuclear envelope protein that physically interacts with and tethers 26S proteasome in the nucleus resulting in the nuclear accumulation of proteasome. Cut8 comprises three functional domains. An N-terminal lysine-rich segment which binds to the proteasome when ubiquitinated, a central dimerization domain and a C-terminal nine-helix, Structure 3q5w, bundle which shows structural similarity to 14-3-3 phosphoprotein-binding domains. The helical bundle is necessary for liposome and cholesterol binding. Cut8 is a proteasome substrate and the N-terminal segment is polyubiquitinated and functions as a degron tag. Ubiquitination of the amino N-terminal segment is essential for the function of Cut8. Lysine residues in the N-terminal segment of Cut8 are required for physical interaction with proteasome. In fission yeast the function of Cut8 has been demonstrated to be regulated by ubiquitin-conjugating Rhp6/Ubc2/Rad6 and ligating enzymes Ubr1. Cut8 homologs have been identified in Drosophila melanogaster, Anopheles gambiae and Dictyostelium discoideum.