The recognition of ubiquitylated substrates is an essential element of ubiqu-itin⁄26S proteasome-mediated proteolysis (UPP), which is mediated directly
by the proteasome subunit RPN10 and⁄or RPN13, or indirectly by ubiquitin
receptors containing ubiquitin-like and ubiquitin-associated domains. By
pull-down and mutagenesis assays, we detected cross-species divergence of
the major recognition pathways.
The truncated C-terminal portion of Bid (tBid) is an important intermedi-ate in ligand-induced apoptosis. tBid has been shown to be sensitive to pro-teasomal inhibitors and downregulated by activation of the epidermal
growth factor (EGF) pathway. Here, we provide evidence that tBid is a
substrate of the ubiquitin ligase Itch, which can specifically interact with
and ubiquitinate tBid, but not intact Bid.
The eye lens is composed of fiber cells that differentiate from epithelial cells
on its anterior surface. In concert with this differentiation, a set of proteins
essential for lens function is synthesized, and the cellular organelles are