Identification of a phylogenetically conserved Sug1 CAD family member that is differentially expressed in the mouse nervous system

The proteasome is a multisubunit protease responsible for degrading proteins conjugated to ubiquitin. The 670-kDa core particle of the proteasome contains the proteolytic active sites, which face an interior chamber within the particle and are thus protected from the cytoplasm. The entry of substrates into this chamber is thought to be governed by the regulatory particle of the proteasome, which covers the presumed channels leading into the interior of the core particle. We have resolved native yeast proteasomes into two electrophoretic variants and have shown that these represent core particles capped with one or two regulatory particles. To determine the subunit composition of the regulatory particle, yeast proteasomes were purified and analyzed by gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Resolution of the individual polypeptides revealed 17 distinct proteins, whose identities were determined by amino acid sequence analysis. Six of the subunits have sequence features of ATPases (Rpt1 to Rpt6). Affinity chromatography was used to purify regulatory particles from various strains, each of which expressed one of the ATPases tagged with hexahistidine. In all cases, multiple untagged ATPases copurified, indicating that the ATPases assembled together into a heteromeric complex. Of the remaining 11 subunits that we have identified (Rpn1 to Rpn3 and Rpn5 to Rpn12), 8 are encoded by previously described genes and 3 are encoded by genes not previously characterized for yeasts. One of the previously unidentified subunits exhibits limited sequence similarity with deubiquitinating enzymes. Overall, regulatory particles from yeasts and mammals are remarkably similar, suggesting that the specific mechanistic features of the proteasome have been closely conserved over the course of evolution.In eukaryotes, the elimination of many short-lived proteins requires their covalent attachment to ubiquitin (43). This pathway is involved in a wide variety of regulatory mechanisms, with substrates including cyclins and CDK inhibitors (49), membrane proteins such as CFTR (104), p53 (84), NF-B (71), c-Fos, c-Jun, and luminal components of the endoplasmic reticulum (9). Multiubiquitin chains target proteins for degradation by the proteasome, an ϳ2-MDa proteolytic complex (reviewed in references 12, 55, 61, and 80).The mechanism of the proteasome is thought to involve unfolding of a protein substrate and translocation from one subcompartment of the enzyme to another prior to degradation. This model is based primarily on the crystal structure of the proteasomal core particle (CP). The CP has a barrel-like shape, with the proteolytic active sites facing the inner chamber, or lumen. In the proteasomal CP from Thermoplasma acidophilum, openings into the lumen are found only at the ends of the barrel (59) and are therefore thought to function as channels for the proteolytic substrate. Because these channels are narrow, it is likely that proteolytic substrates must be unfolded prior to entry into the lumen of the CP. Bas...

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“…All RP subunits identified in the purified preparation from yeast (Fig. 3) have clear homologs in other eukaryotes ( Table 3 (92).…”

Section: Resultsmentioning

confidence: 99%

The Regulatory Particle of the Saccharomyces cerevisiae Proteasome

Glickman

Rubin

Fried

et al. 1998

Molecular and Cellular Biology

471

433

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“…Accession numbers correspond to the proteins in the SwissProt-TrEMBL database (see Table 1 regulation of PCD. For example, ISM death is accompanied by exponential increases in the expression of ubiquitin-proteasome components, including: polyubiquitin (Schwartz et al, 1990b) and 20S and 26S proteasome subunits (Dawson et al, 1995;Jones et al, 1995;Sun et al, 1997). Several of the other genes isolated from the ISMs encode novel genes whose roles are undefined, such as SCLP (Kuelzer et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Acheron, a novel member of the Lupus Antigen family, is induced during the programmed cell death of skeletal muscles in the moth Manduca sexta

Valavanis

Wang

Sun

et al. 2007

Gene

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In order to identify novel genes associated with the initiation of programmed cell death during development, we employed a differential screening protocol to isolate cDNAs that were induced when the intersegmental muscles (ISM) of the moth Manduca sexta become committed to die at the end of metamorphosis. In this report we provide the first description of Acheron (Achn), a novel protein that was isolated in this screen. Acheron contains three Lupus antigen (La) repeats, nuclear localization and export (NLS and NES) signals, and an RNA recognition motif. Achn defines a new subfamily of La proteins that appears to have branched from authentic La protein relatively late in metazoan evolution. Achn is widely expressed in various insect, mouse and human tissues. Consistent with its expression during ISM death, Achn has been shown in separate studies to control muscle differentiation and apoptosis in both mice and zebrafish. These data define Achn as a newly discovered regulatory molecule that presumably mediates a variety of developmental and homeostatic processes in animals.

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“…It is not known whether this codon can serve as an alternative start site for translation. However, it is worth noting that the vast majority of the sequence variation between SUG1 genes in dierent taxa is restricted to the N-terminal end of the encoded protein (Sun et al 1997).…”

Section: Resultsmentioning

confidence: 99%

“…We did not observe this latter pattern of expression, which may re¯ect dierences between expression of 20S versus 26S forms. While the mouse SUG1 homolog M56 is expressed in all tissues, expression is highest within the brain (Sun et al 1997). M56 expression in the mouse brain is not uniform: it is seen predominantly in neurons of the olfactory bulb, the hippocampus and the cerebellum.…”

Section: Discussionmentioning

confidence: 99%

“…Recent studies have revealed that the SUG1 protein exhibits direct interactions with components of Mol Gen Genet (1998) 259: 13±20 the transcriptional and DNA repair pathways, and that it possesses DNA helicase activity (Wang et al 1996;Fraser et al 1997;Weeda et al 1997), although how this latter property relates to its role in the 26S proteasome is not understood. Recently, homologs of SUG1 have been cloned from several taxa, including: Trip1 from human (Lee et al 1995); m56 (Sun et al 1997)/mSUG1 (vom Baur et al 1996/FZA±B (Wang et al 1996) from mouse, and 18-56 from moth (Sun et al 1996). The 18-56 cDNA was isolated using a cloning paradigm designed to identify genes that are up-regulated during the programmed death of moth skeletal muscle (Schwartz et al 1990;Sun et al 1996).…”

Section: Introductionmentioning

confidence: 99%

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Cloning and characterization of Pros45, the Drosophila SUG1 proteasome subunit homolog

et al. 1998

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The proteasome plays essential roles in a variety of cellular processes, including degradation of the bulk of cellular proteins, degradation of short-lived proteins such as cell cycle regulators, generation of antigenic peptides, and mediating programmed cell death. One of the best characterized subunits of the 26S proteasome is encoded by the yeast gene SUG1. We report here the cloning and characterization of the Drosophila homolog of this gene, Pros45. At the protein level, Pros45 is highly conserved with respect to its homologs in a variety of taxa: it shows 74% identity to yeast Sug1; 86% to mouse m56/mSug1/FZA-B; 87% to human Trip1; and 97% to moth 18-56. Using a genomic clone as a probe for in situ hyridization to polytene chromesomes, we demonstrated that Pros45 maps to 19F, near the base of the X chromosome. Use of a pros45 cDNA clone as a probe revealed a second site of hybridization at 99CD. Pros45 mRNA is found in the unfertilized egg and in all cells of the early embryo. By the end of embryogenesis, Pros45 is expressed predominantly in the central nervous system. Targeted expression of Pros45 in a variety of different cells using the Gal4 UAS P-element system failed to generate an overt phenotype. This study provides the foundation for further examination of the role of the 26S proteasome in homeostasis and development in Drosophila.

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Identification of a phylogenetically conserved Sug1 CAD family member that is differentially expressed in the mouse nervous system

Cited by 10 publications

References 53 publications

The Regulatory Particle of the Saccharomyces cerevisiae Proteasome

The Regulatory Particle of the Saccharomyces cerevisiae Proteasome

Acheron, a novel member of the Lupus Antigen family, is induced during the programmed cell death of skeletal muscles in the moth Manduca sexta

Cloning and characterization of Pros45, the Drosophila SUG1 proteasome subunit homolog

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