Structure of the preholoproteasome reveals late steps in proteasome core particle biogenesis

Walsh, Richard M.; Rawson, Shaun; Schnell, Helena M.; Velez, Benjamin; Rajakumar, Tamayanthi; Hanna, John

doi:10.1038/s41594-023-01081-w

Cited by 4 publications

(1 citation statement)

References 37 publications

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“…Structure 5, the half-CP, reveals the function of the β5 propeptide in completing β-ring assembly and its collaboration with POMP in this process; Structure 5 also shows how the proteasome active sites are restrained prior to fusion with another half-CP. Notably, Structures 3, 4, and the human preholo intermediate also allow comparison to the previously-determined structures of the corresponding yeast 13S, pre-15S, and preholo intermediates 48,61 , not only validating our approach but also revealing conserved and species-specific aspects of proteasome assembly. One particularly striking feature was the overall high degree of structural conservation of POMP, the β2-propeptide, and the β5-propeptide, respectively, despite relatively low sequence similarity between the two species.…”

Section: Discussionsupporting

confidence: 56%

Visualizing chaperone-mediated multistep assembly of the human 20S proteasome

Adolf,

Du,

Goodall

et al. 2024

Preprint

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Dedicated assembly factors orchestrate stepwise production of many molecular machines, including the 28-subunit proteasome core particle (CP) that mediates protein degradation. Here, we report cryo-EM reconstructions of seven recombinant human subcomplexes that visualize all five chaperones and the three active site propeptides across a wide swath of the assembly pathway. Comparison of these chaperone-bound intermediates and a matching mature CP reveals molecular mechanisms determining the order of successive subunit additions, and how proteasome subcomplexes and assembly factors structurally adapt upon progressive subunit incorporation to stabilize intermediates, facilitate the formation of subsequent intermediates, and ultimately rearrange to coordinate proteolytic activation with gated access to active sites. The structural findings reported here explain many previous biochemical and genetic observations. This work establishes a methodologic approach for structural analysis of multiprotein complex assembly intermediates, illuminates specific functions of assembly factors, and reveals conceptual principles underlying human proteasome biogenesis.

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Section: Discussionsupporting

confidence: 56%

Visualizing chaperone-mediated multistep assembly of the human 20S proteasome

Adolf,

Du,

Goodall

et al. 2024

Preprint

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Structural basis of human 20S proteasome biogenesis

Zhang,

Zhou,

Mohammad

et al. 2024

Nat Commun

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New proteasomes are produced to accommodate increases in cellular catabolic demand and prevent the accumulation of cytotoxic proteins. Formation of the proteasomal 20S core complex relies on the function of the five chaperones PAC1-4 and POMP. Here, to understand how these chaperones facilitate proteasome assembly, we tagged the endogenous chaperones using CRISPR/Cas gene editing and examined the chaperone-bound complexes by cryo-EM. We observe an early α-ring intermediate subcomplex that is stabilized by PAC1-4, which transitions to β-ring assembly upon dissociation of PAC3/PAC4 and rearrangement of the PAC1 N-terminal tail. Completion of the β-ring and dimerization of half-proteasomes repositions critical lysine K33 to trigger cleavage of the β pro-peptides, leading to the concerted dissociation of POMP and PAC1/PAC2 to yield mature 20S proteasomes. This study reveals structural insights into critical points along the assembly pathway of the human proteasome and provides a molecular blueprint for 20S biogenesis.

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