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  • 1
    Language: English
    In: Molecular Cell, 2010, Vol.38(6), pp.879-888
    Description: The 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. ► 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
    Keywords: Proteins ; Biology
    ISSN: 1097-2765
    E-ISSN: 1097-4164
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  • 2
    Language: English
    In: The Journal of biological chemistry, 03 September 2004, Vol.279(36), pp.37751-62
    Description: 26 S proteasomes fulfill final steps in the ubiquitin-dependent degradation pathway by recognizing and hydrolyzing ubiquitylated proteins. As the 26 S proteasome mainly localizes to the nucleus in yeast, we addressed the question how this 2-MDa multisubunit complex is imported into the nucleus. 26 S proteasomes consist of a 20 S proteolytically active core and 19 S regulatory particles, the latter composed of two subcomplexes, namely the base and lid complexes. We have shown that 20 S core particles are translocated into the nucleus as inactive precursor complexes via the classic karyopherin alphabeta import pathway. Here, we provide evidence that nuclear import of base and lid complexes also depends on karyopherin alphabeta. Potential classic nuclear localization sequences (NLSs) of base subunits were analyzed. Rpn2 and Rpt2, a non-ATPase subunit and an ATPase subunit of the base complex, harbor functional NLSs. The Rpt2 NLS deletion yielded wild type localization. However, the deletion of the Rpn2 NLS resulted in improper nuclear proteasome localization and impaired proteasome function. Our data support the model by which nuclear 26 S proteasomes are assembled from subcomplexes imported by karyopherin alphabeta.
    Keywords: Nuclear Localization Signals ; Cell Nucleus -- Metabolism ; Proteasome Endopeptidase Complex -- Metabolism ; Saccharomyces Cerevisiae Proteins -- Metabolism ; Alpha Karyopherins -- Metabolism ; Beta Karyopherins -- Metabolism
    ISSN: 0021-9258
    E-ISSN: 1083351X
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  • 3
    Language: English
    In: Journal of Molecular Biology, 2002, Vol.317(3), pp.401-413
    Description: The mechanism by which yeast 20 S proteasomes are imported into the nucleus is still unresolved. Here, we provide the first evidence that 20 S proteasomes are imported as precursor complexes into the nucleus. By using the srp1-49 mutant which is deficient in nuclear import of cargos with classical nuclear localization sequences (cNLS), we show that proteasome precursor complexes associate with importin/karyopherin alpha beta , the cNLS receptor, and that they accumulate inside the cytoplasm. Reconstitution assays revealed that only precursor complexes are targeted to the nuclear envelope (NE) by karyopherin alpha beta . In support, the green fluorescent protein (GFP)-labelled maturation factor Ump1, marking precursor complexes, mainly localizes to the nucleus and around the NE. Our data suggest that nuclear 20 S proteasomes are finally matured inside the nucleus. Copyright 2002 Elsevier Science Ltd.
    Keywords: 20 S Proteasome Biogenesis ; Nuclear Import ; Yeast ; Biology ; Chemistry
    ISSN: 0022-2836
    E-ISSN: 1089-8638
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  • 4
    In: EMBO reports, January 2009, Vol.10(1), pp.101-101
    ISSN: 1469-221X
    E-ISSN: 1469-3178
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  • 5
    In: EMBO reports, December 2008, Vol.9(12), pp.1237-1243
    Description: Blm10, a crucial protease of eukaryotic cells, is bound to yeast proteasome core particles (CPs). Two gates, at both ends of the CP, control the access of protein substrates to the catalytic cavity of the CP. Normally, substrate access is auto‐inhibited by a closed gate conformation unless regulatory complexes are bound to the CP and translocate protein substrates in an ATP‐dependent manner. Here, we provide evidence that Blm10 recognizes pre‐activated open gate CPs, which are assumed to exist in an equilibrium with inactive closed gate CP. Consequently, single‐capped Blm10‐CP shows peptide hydrolysis activity. Under conditions of disturbed CP assembly, as well as in open gate mutants, pre‐activated CP or constitutively active CP, respectively, prevail. Then, Blm10 sequesters disordered and open gate CP by forming double‐capped Blm10‐CP in which peptide hydrolysis activity is repressed. We conclude that Blm10 distinguishes between gate conformations and regulates the activation of CP.
    Keywords: Medicine ; Biology;
    ISSN: 1469-221X
    E-ISSN: 1469-3178
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  • 6
    In: GBM Fall meeting Hamburg 2007, 9/2007, Vol.2007(Fall)
    ISSN: GBM Fall meeting Hamburg 2007
    Source: Elsevier Miscellaneous (via CrossRef)
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