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.