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)

The specificity of 26S proteasomes' endoribonuclease activity has been shown to be changed under effect of erythroid differentiation (hemin) and programmed cell death (diethylmaleate) inductors in proerythroleukemic K562 cells. Treatment of K562 cells with apoptosis and differentiation inductors leads to the specific stimulation of RNase activity towards certain mRNA and to reduction of proteasome RNase activity towards other mRNA. The enzymatic activity under study has been demonstrated to be specifically and selectively dependent on phosphorylation of 26S proteasome subunits as well as on Mg and Ca ions. The conclusion is drawn that the specificity of the proteasomes' RNAse activity is regulated during differentiation and apoptosis, and selective regulation of the activity of different nuclease centers is suggested, the mechanism involving changes in phosphorylation of proteasome subunits and cation homeostasis.
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PMID:[Regulation of the 26S proteasomes' endoribonuclease activity specificity in k562 cells under effect of differentiation and apoptosis inductors]. 1743 99

Human immunodeficiency virus type 1 (HIV-1) Vif counteracts the antiviral activity of the human cytidine deaminase APOBEC3G (APO3G) by inhibiting its incorporation into virions. This has been attributed to the Vif-induced degradation of APO3G by cytoplasmic proteasomes. We recently demonstrated that although APO3G has a natural tendency to form RNA-dependent homo-multimers, multimerization was not essential for encapsidation into HIV-1 virions or antiviral activity. We now demonstrate that a multimerization-defective APO3G variant (APO3G C97A) is able to assemble into RNase-sensitive high-molecular-mass (HMM) complexes, suggesting that homo-multimerization of APO3G and assembly into HMM complexes are unrelated RNA-dependent processes. Interestingly, APO3G C97A was highly resistant to Vif-induced degradation even though the two proteins were found to interact in coimmunoprecipitation experiments and exhibited partial colocalization in transfected HeLa cells. Surprisingly, encapsidation and antiviral activity of APO3G C97A were both inhibited by Vif despite resistance to degradation. These results demonstrate that targeting of APO3G to proteasome degradation and interference with viral encapsidation are distinct functional properties of Vif.
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PMID:Human immunodeficiency virus type 1 Vif inhibits packaging and antiviral activity of a degradation-resistant APOBEC3G variant. 1752 11

The polysomal ribonuclease 1 (PMR1) mRNA endonuclease forms a selective complex with its translating substrate mRNAs where it is activated to initiate mRNA decay. Previous work showed tyrosine phosphorylation is required for PMR1 targeting to this polysome-bound complex, and it identified c-Src as the responsible kinase. c-Src phosphorylation occurs in a distinct complex, and the current study shows that 90-kDa heat shock protein (Hsp90) is also recovered with PMR1 and c-Src. Hsp90 binding to PMR1 is inhibited by geldanamycin, and geldanamycin stabilizes substrate mRNA to PMR1-mediated decay. PMR1 is inherently unstable and geldanamycin causes PMR1 to rapidly disappear in a process that is catalyzed by the 26S proteasome. We present a model where Hsp90 interacts transiently to stabilize PMR1 in a manner similar to its interaction with c-Src, thus facilitating the tyrosine phosphorylation and targeting of PMR1 to polysomes.
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PMID:The 90-kDa heat shock protein stabilizes the polysomal ribonuclease 1 mRNA endonuclease to degradation by the 26S proteasome. 1804 90

S-RNase-based self-incompatibility has been identified in three flowering plant families, including the Solanaceae, and this self/non-self recognition mechanism between pollen and pistil is controlled by two polymorphic genes at the S-locus, S-RNase and S-locus F-box (SLF). S-RNase is produced in the pistil and taken up by pollen tubes in a non-S-haplotype-specific manner. How an allelic product of SLF interacts with self and non-self S-RNases to result in growth inhibition of self pollen tubes is not completely understood. One model predicts that SLF targets non-self S-RNases for ubiquitin/26S proteasome-mediated degradation, thereby only allowing self S-RNase to exert cytotoxic activity inside a pollen tube. To test this model, we studied whether any of the 20 lysine residues in S(3)-RNase of Petunia inflata might be targets for ubiquitination. We identified six lysines near the C-terminus for which mutation to arginine significantly reduced ubiquitination and degradation of the mutant S(3)-RNase, GST:S(3)-RNase (K141-164R) in pollen tube extracts. We further showed that GST:S(3)-RNase (K141-164R) and GST:S(3)-RNase had similar RNase activity, suggesting that their degradation was probably not caused by an ER-associated protein degradation pathway that removes mis-folded proteins. Finally, we showed that PiSBP1 (P. inflata S-RNase binding protein 1), a potential RING-HC subunit of the PiSLF (P. inflata SLF)-containing E3-like complex, could target S-RNase for ubiquitination in vitro. All these results suggest that ubiquitin/26S proteasome-dependent degradation of S-RNase may be an integral part of the S-RNase-based self-incompatibility mechanism.
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PMID:Identification of major lysine residues of S(3)-RNase of Petunia inflata involved in ubiquitin-26S proteasome-mediated degradation in vitro. 1834 91

The objective was to identify proteins differentially expressed in vaginal cancer to elucidate relevant cancer-related proteins. A total of 16 fresh-frozen tissue biopsies, consisting of 5 biopsies from normal vaginal epithelium, 6 from primary vaginal carcinomas and 5 from primary cervical carcinomas, were analysed using two-dimensional gel electrophoresis (2-DE) and MALDI-TOF mass spectrometry. Of the 43 proteins identified with significant alterations in protein expression between non-tumourous and tumourous tissue, 26 were upregulated and 17 were downregulated. Some were similarly altered in vaginal and cervical carcinoma, including cytoskeletal proteins, tumour suppressor proteins, oncoproteins implicated in apoptosis and proteins in the ubiquitin-proteasome pathway. Three proteins were uniquely altered in vaginal carcinoma (DDX48, erbB3-binding protein and biliverdin reductase) and five in cervical carcinoma (peroxiredoxin 2, annexin A2, sarcomeric tropomyosin kappa, human ribonuclease inhibitor and prolyl-4-hydrolase beta). The identified proteins imply involvement of multiple different cellular pathways in the carcinogenesis of vaginal carcinoma. Similar protein alterations were found between vaginal and cervical carcinoma suggesting common tumourigenesis. However, the expression level of some of these proteins markedly differs among the three tissue specimens indicating that they might be useful molecular markers.
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PMID:Differential tissue-specific protein markers of vaginal carcinoma. 1936 86

S-RNase-based self-incompatibility (SI) is a genetically determined self/non-self-recognition process employed by many flowering plant species to prevent inbreeding and promote outcrosses. For the Plantaginaceae, Rosaceae and Solanaceae, it is now known that S-RNase and S-locus F-box (two multiple allelic genes at the S-locus) determine the female and male specificity, respectively, during SI interactions. However, how allelic products of these two genes interact inside pollen tubes to result in specific growth inhibition of self-pollen tubes remains to be investigated. Here, we review all the previously proposed biochemical models and discuss whether their predictions are consistent with all SI phenomena, including competitive interaction where SI breaks down in pollen that carries two different pollen S-alleles. We also discuss these models in light of the recent findings of compartmentalization of S-RNases in both incompatible and compatible pollen tubes. Lastly, we summarize the results from our recent biochemical studies of PiSLF (Petunia inflata SLF) and S-RNase, and present a new model for the biochemical mechanism of SI in the Solanaceae. The tenet of this model is that a PiSLF preferentially interacts with its non-self S-RNases in the cytoplasm of a pollen tube to result in the assembly of an E3-like complex, which then mediates ubiquitination and degradation of non-self S-RNases through the ubiquitin-26S proteasome pathway. This model can explain all SI phenomena and, at the same time, has raised new questions for further study.
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PMID:Biochemical models for S-RNase-based self-incompatibility. 1982 63

The HIV-1 viral infectivity factor (Vif) allows productive infection of non-permissive cells (including most natural HIV-1 targets) by counteracting the cellular cytosine deaminases APOBEC-3G (hA3G) and hA3F. The Vif-induced degradation of these restriction factors by the proteasome has been extensively studied, but little is known about the translational repression of hA3G and hA3F by Vif, which has also been proposed to participate in Vif function. Here, we studied Vif binding to hA3G mRNA and its role in translational repression. Filter binding assays and fluorescence titration curves revealed that Vif tightly binds to hA3G mRNA. Vif overall binding affinity was higher for the 3'UTR than for the 5'UTR, even though this region contained at least one high affinity Vif binding site (apparent K(d) = 27 +/- 6 nM). Several Vif binding sites were identified in 5' and 3'UTRs using RNase footprinting. In vitro translation evidenced that Vif inhibited hA3G translation by two mechanisms: a main time-independent process requiring the 5'UTR and an additional time-dependent, UTR-independent process. Results using a Vif protein mutated in the multimerization domain suggested that the molecular mechanism of translational control is more complicated than a simple physical blockage of scanning ribosomes.
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PMID:HIV-1 Vif binds to APOBEC3G mRNA and inhibits its translation. 1991 Mar 70

26S proteasome is a multisubunit protein complex that plays a pivotal role in protein degradation. Proteasome's enzymatic activities--proteolytic, ATPase/helicase and RNase--can be used in regulation of multiple cellular processes. Recent studies confirm the major role of proteasomes in transcriptional regulation. Although various post-translational modifications of proteasome subunits have been described, relatively little is known about their functional effect on regulation of proteasome-dependent gene expression. In this article, we talk about the role of proteasomes in control of gene expression and different stages of transcription.
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PMID:[Proteasomes and their role in transcriptional regulation]. 2042 96

The ubiquitin/26S proteasome system (UPS) plays a central role in plant protein degradation. Over the past few years, the importance of this pathway in plant-pathogen interactions has been increasingly highlighted. UPS is involved in almost every step of the defence mechanisms in plants, regardless of the type of pathogen. In addition to its proteolytic activities, UPS, through its 20S RNase activity, may be part of a still unknown antiviral defence pathway. Strikingly, UPS is not only a weapon used by plants to defend themselves, but also a target for some pathogens that have evolved mechanisms to inhibit and/or use this system for their own purposes. This article attempts to summarize the current knowledge on UPS involvement in plant-microbe interactions, a complex scheme that illustrates the never-ending arms race between hosts and microbes.
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PMID:The ubiquitin/26S proteasome system in plant-pathogen interactions: a never-ending hide-and-seek game. 2044 78

Activation-induced deaminase (AID) initiates somatic hypermutation, gene conversion and class switch recombination by deaminating variable and switch region DNA cytidines to uridines. AID is predominantly cytoplasmic and must enter the nuclear compartment to initiate these distinct antibody gene diversification reactions. Nuclear AID is relatively short-lived, as it is efficiently exported by a CRM1-dependent mechanism and it is susceptible to proteasome-dependent degradation. To help shed light on mechanisms of post-translational regulation, a yeast-based screen was performed to identify AID-interacting proteins. The calcium and integrin binding protein CIB1 was identified by sequencing and the interaction was confirmed by immunoprecipitation experiments. The AID/CIB1 resisted DNase and RNase treatment, and it is therefore unlikely to be mediated by nucleic acid. The requirement for CIB1 in AID-mediated antibody gene diversification reactions was assessed in CIB1-deficient DT40 cells and in knockout mice, but immunoglobulin gene conversion and class switch recombination appeared normal. The DT40 system was also used to show that CIB1 over-expression has no effect on gene conversion and that AID-EGFP subcellular localization is normal. These combined data demonstrate that CIB1 is not required for AID to mediate antibody gene diversification processes. It remains possible that CIB1 has an alternative, a redundant or a subtle non-limiting regulatory role in AID biology.
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PMID:The interaction between AID and CIB1 is nonessential for antibody gene diversification by gene conversion or class switch recombination. 2065 29


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