The Prosomes (Multicatalytic Proteinases; Proteasomes) and Their Relationship to the Untranslated Messenger Ribonucleoproteins, the Cytoskeleton, and Cell Differentiation

Scherrer, Klaus; Bey, Fayçal

doi:10.1016/s0079-6603(08)60047-1

Cited by 58 publications

(26 citation statements)

References 165 publications

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“…This active-site assignment is in line with previous mutagenesis [47, 49 -51] and inhibitor studies [13]. From the crystallographic structure of the yeast proteasome a potentially new type of active centre has been postulated, which is formed by three to four main-chain carbonyl oxygens at the ends of helix H2 of all seven subunits, together with some water molecules [30].…”

Section: Proteolytic Activitysupporting

confidence: 83%

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Structure and assembly of the 20S proteasome

Gerards¹,

Jong²,

Boelens³

et al. 1998

CMLS, Cell. Mol. Life Sci.

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The barrel-shaped 20S proteasome is one of the two components of a larger 26S particle, the multicatalytic 2000-kDa protease complex. The proteolytic sites are located in the inner chamber of the 20S particle and are only accessible via narrow entrances. This paper reviews the current knowledge concerning proteasome formation, proteolytic activities, structural aspects and assembly. Eukaryotic proteasomes are made up by four rings each of which contains seven different subunits occurring at fixed positions. While the outer rings contain alpha-type subunits, the inner ones comprise beta-type subunits. The current assembly model for eukaryotic 20S proteasomes is based upon the detection of 13S and 16S intermediates, respectively, in addition to previous findings with archaebacterial and eubacterial proteasome assembly. The available data suggest a cooperative assembly of the alpha-type and beta-type subunits into half proteasome-like complexes followed by dimerization into proteasomes. During or after dimerization of half proteasomes, the beta-type subunits are processed. The prosequence of the beta-type subunits is essential for the assembly proves and prevents protease activity of immature proteasomes.

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Section: Proteolytic Activitysupporting

confidence: 83%

“…Reviews toskeleton [13]. Despite the abundance and characteristic properties of the proteasome, progress in understanding the function and mode of action of the particle has, until recently, been slow.…”

Section: Introductionmentioning

confidence: 99%

Structure and assembly of the 20S proteasome

Gerards¹,

Jong²,

Boelens³

et al. 1998

CMLS, Cell. Mol. Life Sci.

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“…The property of HsC8 to form rings may, however, indicate that this subunit can actually occupy several positions in ␣-rings of proteasome(-like) particles, which would result in proteasome subpopulations differing in the content of ␣-type subunits. Such compositional variation could explain why the monoclonal antibody p31k (46), which is directed to HsC8 (47), 3 stained mainly areas in rat liver cells that are close to the bile canaliculi, whereas a much more general staining was obtained with a polyclonal antiserum directed to proteasomes (48,49). Also in C2.7 myoblasts (50), LCLC103 lung carcinoma cells and the adherent fraction of NCI-H524 lung carcinoma cells, 4 and cells in some stages of early embryonic development of the newt Pleurodeles waltl (51), the p31k antibody gave different staining patterns compared with the monoclonal antibodies directed to other ␣-type subunits.…”

Section: Discussionmentioning

confidence: 99%

The Human α-Type Proteasomal Subunit HsC8 Forms a Double Ringlike Structure, but Does Not Assemble into Proteasome-like Particles with the β-Type Subunits HsDelta or HsBPROS26

Gerards

Enzlin

Häner

et al. 1997

Journal of Biological Chemistry

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The eukaryotic proteasome is a barrel-shaped protease complex made up of four seven-membered rings of which the outer and inner rings may contain up to seven different ␣-and ␤-type subunits, respectively. The assembly of the eukaryotic proteasome is not well understood. We cloned the cDNA for HsC8, which is one of the seven known human ␣-type subunits, and produced the protein in Escherichia coli. Recombinant HsC8 protein forms a complex of about 540 kDa consisting of double ringlike structures, each ring containing seven subunits. Such a structure has not earlier been reported for any eukaryotic proteasome subunit, but is similar to the complex formed by the recombinant ␣-subunit of the archaebacterium Thermoplasma acidophilum (Zwickl, P., Kleinz, J., and Baumeister, W. (1994) Nat. Struct. Biol. 1, 765-770). The ability of HsC8 to form ␣-rings suggests that these complexes may play an important role in the initiation of proteasome assembly in eukaryotes. To test this, we used two human ␤-type subunits, HsBPROS26 and HsDelta. Both these ␤-type subunits, either in the proprotein or in the mature form, exist in monomers up to tetramers. In contrast to the ␣-and ␤-subunit of T. acidophilum, coexpression of the human ␤-type subunits with HsC8 does not result in the formation of proteasome-like particles, which would be in agreement with the notion that proteasome assembly in eukaryotes is much more complex than in archaebacteria.

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“…And RNase activity has been described for prosomes (20S proteasomes), but with a different specificity (only for TMV viral RNA) [22,23]. Although we did not study the action of α‐RNPs on this substrate, the existence of several ribonuclease centers in α‐RNP seems to be quite possible (just as there are several proteolytic catalytic centers in proteasomes [24,25]). Endonucleolysis of hnRNA with α‐RNP can be used by eukaryotic cells either for mRNA processing or for degradation of the hnRNA which does not go to the cytoplasm and degrades in the nucleus.…”

Section: Discussionmentioning

confidence: 91%

The specific endoribonuclease activity of small nuclear and cytoplasmic α‐RNPs

et al. 1999

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For the first time small nuclear ribonucleoprotein particles (K K-RNP) tightly bound to chromatin as well as cytoplasmic K K-RNP are shown to possess strong and regulated endonuclease activity specific for mRNAs and hnRNAs. The enzymatic nature of this activity is confirmed, and the optimal conditions detected. This RNase activity is controlled by the action of a differentiating stimulus, dimethylsulfoxide, in human K562 cells. Small K K-RNP involvement in the coordinated control of stability of pre-messenger RNA and messenger RNA molecules is suggested.z 1999 Federation of European Biochemical Societies.

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The Prosomes (Multicatalytic Proteinases; Proteasomes) and Their Relationship to the Untranslated Messenger Ribonucleoproteins, the Cytoskeleton, and Cell Differentiation

Cited by 58 publications

References 165 publications

Structure and assembly of the 20S proteasome

Structure and assembly of the 20S proteasome

The Human α-Type Proteasomal Subunit HsC8 Forms a Double Ringlike Structure, but Does Not Assemble into Proteasome-like Particles with the β-Type Subunits HsDelta or HsBPROS26

The specific endoribonuclease activity of small nuclear and cytoplasmic α‐RNPs

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