Ecm29 Fulfils Quality Control Functions in Proteasome Assembly

SummaryThe proteasome, the central protease of eukaryotic cells, is composed of one core particle (CP) and one or two adjacent regulatory particles (RP), which contain multiple subunits. Several proteasome-dedicated chaperones govern the assembly of CP and RP, respectively. We sought for proteins that regulate final steps of RP-CP assembly in yeast and found Ecm29, a conserved HEAT-like repeat protein. Here, we show that Ecm29 controls the integrity of RP-CP assemblies. Ecm29 recognizes RP-CP species in which CP maturation is stalled due to the lack of distinct β subunits. Reconstitution assays revealed that Ecm29 functions as scaffold protein during the remodeling of incompletely matured RP-CP assemblies into regular enzymes. Upon the completion of CP maturation, Ecm29 is degraded and RP-CP is dissociated.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (113 K)Download as PowerPoint slideHighlights► Ecm29 controls the assembly of proteasomal core (CP) and regulatory (RP) particles ► Ecm29 binds RP-CP configured proteasomes with incompletely matured proteasomes ► In vitro Ecm29-bound proteasomes can be remodeled into regular enzymes