Proteasome, COP9 signalosome

Six of the CSN subunits contain PCI (proteasome, COP9 signalosome, initiation factor 3) domains and two contain MPN (Mpr-Padl-JV-terminal) domains [58]. These two characteristic domains have been found in three protein complexes the CSN, the 26S proteasome lid complex (lid) and the eIF3 complex. The two domains are composed of about 150 to 200 amino acids at the N- or C-terminus of the CSN subunits. Apparently, the PCI domain has been shown to be important for interactions between CSN subunits. Thus, it might have a scaffolding function [22, 59). 

Glickman, M. H., Rubin, D. M., Coux, O., Wefes, I., Pfeifer, G., Cjeka, Z., Baumeister, W., Fried, V. A., and Finley, D. A subcomplex of the proteasome regulatory partide required for ubiquitin-conjugate degradation and related to the COP9-signalosome and eIF3. Cell 1998, 94, 615-623. 

Rety, S., Jalinot, P. Association of the mammalian proto-oncoprotein Int-6 with the three protein complexes eIF3, COP9 signalosome and 26S proteasome. FEBS Lett. 2002, 527,... 

Li, L, Deng, X. W. The COP9 signalosome an alternative lid for the 26 S proteasome Trends Cell Biol. 

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