Rad23 is a member of a novel class of proteins that contain unprocessed ubiquitin-like (UbL) domains. We showed recently that a small fraction of Rad23 can form an interaction with the 26S proteasome. Similarly, a small fraction of Rpn10 is a component of the proteasome. Rpn10 can bind multiubiquitin chains in vitro, but genetic studies have not clarified its role in vivo. We report here that the loss of both Rad23 and Rpn10 results in pleiotropic defects that are not observed in either single mutant, rad23Δ rpn10Δ displays slow growth, cold sensitivity, and a pronounced G2/M phase delay, implicating overlapping roles for Rad23 and Rpn10. Although rad23Δ rpn10Δ displays similar sensitivity to DNA damage as a rad23Δ single mutant, deletion of RAD23 in rpn10Δ significantly increased sensitivity to canavanine, a phenotype associated with an rpn10Δ single mutant. A mutant Rad23 that is unable to bind the proteasome ((ΔUbL)rad23) does not suppress the canavanine or cold-sensitive defects of rad23Δ rpn10Δ, demonstrating that Rad23/proteasome interaction is related to these effects. Finally, the accumulation of multiubiquitinated proteins and the stabilization of a specific proteolytic substrate in rad23Δ rpn10Δ suggest that proteasome function is altered.
|Original language||English (US)|
|Number of pages||11|
|State||Published - Sep 1999|
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