Transfer of Ho endonuclease and Ufo1 to the proteasome by the UbL-UbA shuttle protein, Ddi1, analysed by complex formation in vitro.

ABSTRACT: The F-box protein, Ufo1, recruits Ho endonuclease to the SCF(Ufo1) complex for ubiquitylation. Both ubiquitylated Ho and Ufo1 are transferred by the UbL-UbA protein, Ddi1, to the 19S Regulatory Particle (RP) of the proteasome for degradation. The Ddi1-UbL domain binds Rpn1 of the 19S RP, the Ddi1-UbA domain binds ubiquitin chains on the degradation substrate. Here we used complex reconstitution in vitro to identify stages in the transfer of Ho and Ufo1 from the SCF(Ufo1) complex to the proteasome. We report SCF(Ufo1) complex at the proteasome formed in the presence of Ho. Subsequently Ddi1 is recruited to this complex by interaction between the Ddi1-UbL domain and Ufo1. The core of Ddi1 binds both Ufo1 and Rpn1; this interaction confers specificity of SCF(Ufo1) for Ddi1. The substrate-shie

SUBMITTER: Voloshin O 

PROVIDER: S-EPMC3398040 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature