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.
Le Tallec
Benoît
B
Laboratoire du Métabolisme de l'ADN et Réponses aux Génotoxiques, SBIGeM, CEA, iBiTecS, Gif-sur-Yvette, F-91191, France.
Barrault
Marie-Bénédicte
MB
Guérois
Raphaël
R
Carré
Thibault
T
Peyroche
Anne
A
D000251:Adenosine Triphosphatases / Q000378:metabolism; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D018832:Molecular Chaperones; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction; D013329:Structure-Activity Relationship
D004268:DNA-Binding Proteins; C112193:HSM3 protein, S cerevisiae; D018832:Molecular Chaperones; C114551:NAS6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D046988:Proteasome Endopeptidase Complex; C119011:26S proteasome non-ATPase regulatory subunit 13; D000251:Adenosine Triphosphatases; C084493:RPT1 protein, S cerevisiae