Mechanism of proteasome gate modulation by assembly chaperones Pba1 and Pba2

Schnell, Helena M.; Ang, Jessie; Rawson, Shaun; Walsh, Richard M.; Micoogullari, Yagmur; Hanna, John

doi:10.1016/j.jbc.2022.101906

Cited by 5 publications

(2 citation statements)

References 31 publications

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“…Importantly, Structure 3 corresponds to the well-recognized 13S precursor 34,45 , and is largely superimposable on the yeast 13S 48 , although there are some notable species-specific differences. First, while the N-termini of both PAC1 and yeast Pba1 are threaded through the open gate into the CP interior, in yeast it is the N-terminus of α2 56 , (not α1) that runs alongside Pba1’s N-terminus into the CP interior (Extended Data Fig. 3e).…”

Section: Resultsmentioning

confidence: 99%

“…This strikingly contrasts from mature isolated CP, where α-subunit N-termini extend into and block access to central pore 2 . Some proteasome activators trigger gate opening via their C-terminal HbYX motifs that insert into pockets between adjacent α-subunits 10,11,[15][16][17]56 . PAC1 contains a conserved, canonical HbYX motif (Ile-Tyr-Thr), which is inserted into the α5/α6 pocket (Fig.…”

Section: Structure 1: α-Ring Stabilization and β-Ring Initiation Thro...mentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

Section: Structure 1: α-Ring Stabilization and β-Ring Initiation Thro...mentioning

confidence: 99%

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

Adolf,

Du,

Goodall

et al. 2024

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

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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