Regulation of Ubiquitin Conjugate Formation

In general, and including all its activities, intrinsic as well as associated, the CSN seems to be a regulator of ubiquitination. Deneddylation, deubiquitination as well 

Interestingly, there are no reports of interactions between the 26S proteasome lid complex and Ub ligases. Known E3s directly interacting with the 26S proteasome seem to bind via base ATPases [88, 89]. This is an interesting functional difference between the CSN and the lid developed during evolution. 

In an alternative model the CSN might be the platform for complete proteolysis. 

It forms supercomplexes consisting of both the ubiquitinating and the proteolytic machineries. According to this model, the substrate first binds to the CSN, is then ubiquitinated by the associated Ub ligase and finally directly charmeled into the 26S proteasome. Deneddylation, deubiquitination and phosphorylation are necessary to maintain the supercomplex, to protect the intermediates and to stimulate proteolysis. 

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