| Modification Notes |
The proteasome is a multisubunit protease responsible for degrading proteins conjugated to ubiquitin (1). Substrates are targeted for proteolysis by the ubiquitin pathway by the addition of a polyubiquitin chain before being degraded by the 26S proteasome (2). The 26S proteasome is made up of two subunits, the 20S proteolytic subunit and the 19S regulatory particle, which recognizes and unfolds ubiquitinated proteins (1). The ubiquitinlike domains (Ubls) of Ubiquitin-like proteins Rad23 and Dsk2 bind both polyubiquitin chains and the 19S regulatory particle (RP) of the 26S proteasome (3). The Ubl domain mediates the binding of Rad23 to proteasomes, which in turn promotes DNA repair and modulates protein degradation, possibly by delivering ubiquitinylated cargo to proteasomes (4). Rad23 binds proteasomes by directly interacting with the base subcomplex of the regulatory particle of the proteasome (4). A component of the base, Rpn1, specifically recognizes the UBL domain of Rad23 through its leucine-rich-repeat-like (LRR-like) domain (4). Rpn1, for regulatory-particle non-ATPase subunit 1, is one of the largest subunits of proteasome (5). Base subunit Rpn10, however, does not mediate the binding of UBL proteins to the proteasome in yeast, although it can contribute to the binding of ubiquitin chains by intact proteasomes (4). |
