Hsm3/S5b participates in the assembly pathway of the 19S regulatory particle of the proteasome.
The 26S proteasome, the central enzyme of the ubiquitin-proteasome system, is comprised of the 20S catalytic core particle (CP) and the 19S regulatory particle (RP), itself composed of two subcomplexes, the base and the lid. 20S proteasome assembly is assisted by several chaperones. Integral subunits of the RP participate in ... its assembly, but no external factors have been identified so far. Here we characterize the yeast Hsm3 protein, which displays unique features regarding 19S assembly. Hsm3 associates with 19S subcomplexes via a carboxy-terminal domain of the Rpt1 base subunit but is missing in the final 26S proteasome. Moreover, Hsm3 is specifically required for the base subcomplex assembly. Finally, we identify the putative species-specific 19S subunit S5b as a functional homolog of the Hsm3 chaperone in mammals. These findings shed light on chaperone-assisted proteasome assembly in eukaryotes.
Mesh Terms:
Adenosine Triphosphatases, Conserved Sequence, DNA-Binding Proteins, Humans, Models, Biological, Molecular Chaperones, Proteasome Endopeptidase Complex, Protein Structure, Tertiary, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Signal Transduction, Structure-Activity Relationship
Adenosine Triphosphatases, Conserved Sequence, DNA-Binding Proteins, Humans, Models, Biological, Molecular Chaperones, Proteasome Endopeptidase Complex, Protein Structure, Tertiary, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Signal Transduction, Structure-Activity Relationship
Mol. Cell
Date: Feb. 13, 2009
PubMed ID: 19217412
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