Identification of a 26S proteasome-associated UCH in fission yeast

We have identified a 26S proteasome-associated ubiquitin carboxyl-terminal hydrolase (UCH) in Schizosaccharomyces pombe, The gene (designated uch2(+)) encodes a protein containing a UCH catalytic domain at its N-terminus and a short extension at its C-terminus. uch2(+) is nonessential as the uch2 nu b mutant strain showed no significant difference from the wild-type strain. The GFP-tagged Uch2p is localized predominantly to the nuclear periphery, which is similar to the 26S proteasome localization. Deletion of the C-term inal extension of Uch2p resulted in a drastic change of its subcellular loc alization: it showed a generally diffused distribution instead of a perinuc lear pattern. Glycerol gradient centrifugation analysis and coimmunoprecipi tation studies of fission yeast extracts using anti-Mts4p antiserum suggest that Uch2p is associated with the 26S proteasome and the association of Uc h2p with the 26S proteasome is mediated by its C-terminal extension. (C) 20 00 Academic Press.