Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prosomes are mRNA-associated RNP particles and cofactors of untranslated (ribosome-) free mRNP having a multicatalytic proteinase (MCP; proteasome) activity. The expression of prosomal proteins in fetal development of the rat liver was investigated by indirect immunofluorescence, using a panel of monoclonal antibodies to individual prosomal proteins (p-mAbs). In all fetal and adult stages tested, strong immunofluorescence staining was observed with the p31K-specific p-mAb exclusively, whilst Western blot analysis showed reactivity also with the p27K and p33K antigens. Double labeling with the 31K p-mAb and an anti-cytokeratin antibody showed that the prosome antigen superimposes partially onto this type of intermediate filaments (IF), confirming earlier observations made on cultured cell lines of various types. Most interestingly, the p31K antigen was found preferentially in the pericanalicular zone of hepatocytes in the developing liver, from day 17 onwards up to the adult state. This shows a preferential concentration of prosomes of a specific type, including the p31K antigen, in the morphologically and possibly functionally specialized apical domain of the hepatocyte, in a differentiation-related fashion.
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PMID:Immunolocalization of a specific type of prosome close to the bile canaliculi in fetal and adult rat liver. 163 91

Prosomes and heat shock protein (HSP) complexes isolated from the cytoplasm of Drosophila cells in culture were biochemically and immunologically characterized. The two complexes were found to separate on sucrose gradients, allowing the analysis of their protein constituents by two-dimensional polyacrylamide gel electrophoresis and by reaction with anti-HSP sera and prosome-specific monoclonal antibodies. All of the prosomal proteins were found to be clearly distinct from the HSP; none of the prosomal proteins was synthesized de novo in heat shock. However, an antiprosome (anti-p27K) monoclonal antibody (mouse anti-duck) recognizing the Drosophila p29K prosomal protein allowed immunoprecipitation from a heat-shocked postmitochondrial supernatant of the crude HSP complex, including the low- and the high-molecular-weight components, in particular the 70 x 10(3)-molecular weight HSP. The highly purified small 16S HSP complex still contained this preexistent p29K prosomal protein, which thus also seems to be a metabolically stable constituent of the HSP complex. The significance of this structural and possibly functional relationship between prosomes and HSP, involving the highly ubiquitous and evolutionarily conserved prosomal protein p27/29K, remains to be elucidated.
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PMID:Prosomes and heat shock complexes in Drosophila melanogaster cells. 250 9

Monoclonal antibodies demonstrated high conservation during evolution of a prosomal protein of M(r) 27,000 and differentiation--specific expression of the epitope. More than 90% of the reacting antigen was found as a p27K protein in the free messenger ribonucleoprotein (mRNP) fraction but another protein of M(r) 38,000, which shared protease fingerprint patterns with the p27K polypeptide, was also labelled in the nuclear and polyribosomal fractions. Sequencing of cDNA recombinant clones encoding the p27/38K protein and comparison with another prosomal protein, p30-33K, demonstrated the existence of a common characteristic sequence pattern containing three highly conserved segments. The genes Hs PROS-27 and Hs PROS-30 were mapped to chromosomes 14 (14q13) and 11 (11p15.1), respectively. The structure of the p27K protein shows multiple potential phosphorylation sites, an NTP-binding fold and an RNA-binding consensus sequence. The Hs PROS-27/beta-galactosidase fusion protein binds a single RNA of about 120 nucleotides from total HeLa cell RNA. Sequence comparisons show that the Hs PROS-27 and Hs PROS-30 genes belong to the gene family that encodes the prosome--MCP (multicatalytic proteinase)--proteasome proteins. Comparison with other members of the family from various species allowed us to show that the tripartite consensus sequence characteristic of the alpha-type sub-family is conserved from archeobacteria to man. The members of this gene family are characterised by very high evolutionary conservation of amino acid sequences of homologous genes and 20%-35% sequence similarity, between different family member within the same species and are clearly distinct from the beta-type family.
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PMID:The prosomal RNA-binding protein p27K is a member of the alpha-type human prosomal gene family. 768 Nov 38

The presence of prosome proteins (p25K and p27K) was shown and their distribution was studied in oogenesis of Xenopus laevis using immunoblotting and immunofluorescence. These proteins form numerous granular clusters of variable size all over the cell. At previtellogenic stages, the prosome antibodies homogeneously stain the oocyte nucleus and the evenly distributed relatively large clusters in the cytoplasm. As the oocyte grows, the pattern of distribution of the prosome proteins undergoes changes: animal-vegetal and cortical gradients appear in the cytoplasm. In the course of oocyte maturation the size of clusters diminishes. Artificial activation of the egg leads to a dorso-ventral gradient in distribution of the prosome proteins. In this way, specific localization of prosome proteins is first visualized during formation of the dorso-ventral polarity. Co-localization of prosome proteins and actin and myosin was found in the oocyte by double staining. Small clusters of prosomes dispersed in the cytoplasm acquire capability of movement (after artificial activation) due, in all likelihood, to persisting connection with the acto-myosin complex of the egg.
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PMID:Distribution of prosome proteins and their relationship with the cytoskeleton in oogenesis of Xenopus laevis. 817 2

Prosomes, also called "multicatalytic proteinase" (MCP) or "proteasomes," are a new type of ubiquitous RNP particle present in some archeobacteria and in all eukaryotic cells tested from yeast to human. They were discovered as subcomplexes of untranslated messenger-ribonucleoproteins (mRNP) and later found to have a MCP activity putatively involved in antigen processing. Being composed of variable sets of characteristic proteins and associating small RNAs (pRNA), families of individual "mosaic" prosome particles seem to characterize the differentiation type and physiological state of individual cells and tissues. Here, prosomes from human lymphocytes, isolated and characterized biochemically and by Western blot analysis, were found to differ in their subunit composition compared to other human prosomes. Surprisingly, prosomal antigens were discovered at the outer surface of blood cells monitored by flow cytometry with monoclonal antibodies to individual prosomal proteins. It was observed that human T and B lymphocytes have variable and characteristic prosomal antigens at their surface according to their CD classification. Interestingly, the lymphocyte subpopulations most strongly labeled by the anti-p25K and anti-p27K mAbs were the NK and B cells.
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PMID:Characterization of prosomes in human lymphocyte subpopulations and their presence as surface antigens. 905 11

The subunit composition of cell-internal and surface prosomes during phorbol myristate acetate (PMA)-induced differentiation of human leukemic T lymphocytes (CCRF-CEM cell line) was studied in relation to clusters of differentiation (CD) markers. PMA inhibited cell growth and decreased the amounts of CD1a and CD4 while CD3, CD8, CD25, CD45, CD57 and MHCI increased it; the p53 anti-oncogene increased while actin levels remained constant. Cells incubated with the inducer PMA for 3 days and placed in fresh inhibitor-free medium resumed growth at a low rate, while the CD values slowly reverted to those of the initial phenotype. The presence and relative amounts of prosome subunits were analyzed by flow cytometry, light and fluorescent microscopy and Western blotting using 3 monoclonal antibodies (p25K, p27K and p30-33K MAbs). The decrease in cytoplasmic antigens on day 3 was remarkable (cells followed for 7 days) while increased surface antigens were observed. Changes in the subcellular distributions of prosome antigens, particularly the p25K and p30-33K subunit, were correlated with a partial arrest of the cell cycle. Interestingly, the composition of cell internal and surface prosomes showed different patterns of change.
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PMID:Changes in the subunit distribution of prosomes (MCP-proteasomes) during the differentiation of human leukemic cells. 924 91

20S proteasomes (prosomes/multicatalytic proteinase) are protein particles built of 28 subunits in variable composition. We studied the changes in proteasome subunit composition during the differentiation of U937 cells induced by phorbol-myristate-acetate or retinoic acid plus 1,25-dihydroxy-cholecalciferol by western blot, flow cytometry and immuno-fluoresence. p25K (C3), p27K (IOTA) and p30/33K (C2) subunits were detected in both the nucleus and cytoplasm of undifferentiated cells. Flow cytometry demonstrated a biphasic decrease in proteasome subunits detection during differentiation induced by RA + VD. PMA caused an early transient decrease in these subunits followed by a return to their control level, except for p30/33K, which remained low. Immuno-fluorescence also showed differences in the cytolocalization of the subunits, with a particular decrease in antigen labeling in the nucleus of RA + VD-induced cells, and a scattering in the cytoplasm and a reorganization in the nucleus of PMA-induced cells. Small amounts of proteasomal proteins were seen on the outer membrane of non-induced cells; these membrane proteins disappeared when treated with RA + VD, whereas some increased on PMA-induced cells. The differential changes in the distribution and type of proteasomes in RA + VD and PMA-induced cells indicate that, possibly, 20S proteasomes may play a role in relation to the mechanisms of differentiation and the inducer used.
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PMID:Proteasome (prosome) subunit variations during the differentiation of myeloid U937 cells. 949 51

Monoclonal antibodies were raised against the prosomal proteins p27K, p29K and the prosome-like protein p21K (PLP) from normal breast glandular cells and from benign and malignant tumors. They were used to clarify the involvement of prosomes in tumorigenesis of human breast cells. Immunostaining showed the distribution of prosomes in the cytoplasm and nuclei of cells from European normal women (EN) and Parsi (P) and non-Parsi (NP) benign (B) and malignant (M) tissues. The flow-cytometry studies showed an increased mean percentage of labeled cells, particularly with anti-p27K prosomal protein mAb, in malignant tissue from NP compared to EN. The p21K data indicated an increase in the number of cells labeled by flow-cytometry studies in all groups compared to EN, while p29K-expressing cells were more abundant in NPN, PB, PM and NPM. Intergroup comparison showed that the mean percentage of cells labeled with anti-p27K and anti-p29K was significantly higher in PB than in NPB, as seen by flow cytometry, whereas there was a higher production or accumulation of the p21K (PLP) prosomal protein in NPM than in PM, as seen by immunostaining. By comparison with EN, there were also significantly more normal cells containing the three antigens in the apparently normal tissue in the neighborhood of the tumor in NPM, and more cells containing p21K in PM patients than in EN. As prosomes are involved in the cell differentiation and in the cell cycle control, the changes observed in breast tissues may be related to oncogenic processes. Furthermore, the modified subunit pattern of prosomes in cancer and, possibly, pre-cancer tissue may be of interest for diagnosis purposes.
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PMID:Increased prosomal proteins in breast cancer cells and in neighboring normal cells in Parsi and non-Parsi populations. 965 95

Myogenesis proceeds by fusion of proliferating myoblasts into myotubes under the control of various transcription factors. In adult skeletal muscle, myogenic stem cells are represented by the satellite cells which can be cultured and differentiate in vitro. This system was used to investigate the subcellular distribution of a particular type of prosomes at different steps of the myogenic process. Prosomes constitute the MCP core of the 26S proteasomes but were first observed as subcomplexes of the untranslated mRNPs; recently, their RNase activity was discovered. A monoclonal antibody raised against the p27K subunit showed that the p27K subunit-specific prosomes move transiently into the nucleus prior to the onset of myoblast fusion into myotubes; this represents possibly one of the first signs of myoblast switching into the differentiation pathway. Prior to fusion, the prosomes containing the p27K subunit return to the cytoplasm, where they align with the gradually formed lengthwise-running desmin-type intermediate filaments and the microfilaments, co-localizing finally with the actin bundles. The prosomes progressively form discontinuous punctate structures which eventually develop a pseudo-sarcomeric banding pattern. In myotubes just formed in vitro, the formation of this pattern seems to preceed that produced by the muscle-specific sarcomeric (alpha)-actin. Interestingly, this pattern of prosomes of myotubes in terminal in vitro differentiation was very similar to that of prosomes observed in vivo in foetal and adult muscle. These observations are discussed in relation to molecular myogenesis and prosome/proteasome function.
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PMID:Dynamic distribution and formation of a para-sarcomeric banding pattern of prosomes during myogenic differentiation of satellite cells in vitro. 1019 81

Prosomes were originally identified as 20S particles associated with untranslated mRNA; they also constitute the core of the 26S proteasomes. The cellular distribution of three types of prosomes characterized by the presence of subunits with molecular masses of 23, 27, and 30 kDa was analyzed using an immunocytochemical approach on cultured chicken erythroblasts. The prosomes containing the p27K and p30K subunits were found in diffuse distribution in both nuclei and cytoplasm. In contrast, the prosomes containing the p23K subunit, although relatively rare in the nuclear space, were found concentrated in one or two large spots. Using in situ hybridization with an alpha(A)-globin gene-specific riboprobe we found that the p23K-type prosomes colocalize in the nucleus with centers of globin (pre-)mRNA processing, and of mRNA accumulation in the cytoplasm. This result suggests there is local coincidence of specific-type prosome function with processing and, possibly, transport of a particular kind of (pre-)mRNA.
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PMID:In the nucleus and cytoplasm of chicken erythroleukemic cells, prosomes containing the p23K subunit are found in centers of globin (pre-)mRNA processing and accumulation. 1041 9


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