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 ataxia mutation (axJ) is a recessive neurological mutation that results in reduced growth, ataxia, and hindlimb muscle wasting in mice. The axJ gene encodes ubiquitin-specific protease 14 (Usp14), a deubiquitinating enzyme (DUB) that associates with the proteasome via its ubiquitin-like (Ubl) domain and is involved in processing ubiquitin chains. Analysis of Usp14 gene products demonstrated that Usp14 undergoes alternative pre-mRNA splicing to produce a full-length form of Usp14 that is capable of binding proteasomes and a form that contains a deletion in the Ubl domain. The full-length form of Usp14 is the only form that appears to be reduced in the axJ mice. Transgenic rescue of the axJ mice with neuronal-specific expression of Usp14 demonstrated that the full-length form of Usp14 was sufficient to restore viability and motor system function to the axJ mice. Biochemical analysis showed that the ubiquitin hydrolyase activity of this form of Usp14 is dependent on the presence of proteasomes, and neuronal expression of full-length Usp14 was able to restore the levels of monomeric ubiquitin in the brains of axJ mice. However, the axJ-rescued mice still displayed the Purkinje cell axonal swellings that are seen in the axJ mice, indicating that this cerebellar alteration is not the primary cause of the axJ movement disorders. These results show that the motor defects observed in the axJ mice are attributable to a neuropathic disease rather than to a muscular disorder and suggest that changes in proteasomal function may contribute to neurological dysfunction in the axJ mice.
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PMID:Transgenic rescue of ataxia mice with neuronal-specific expression of ubiquitin-specific protease 14. 1707 71

The spindle checkpoint prevents chromosome mis-segregation by delaying sister chromatid separation until all chromosomes have achieved bipolar attachment to the mitotic spindle. Its operation is essential for accurate chromosome segregation, whereas its dysregulation can contribute to birth defects and tumorigenesis. The target of the spindle checkpoint is the anaphase-promoting complex (APC), a ubiquitin ligase that promotes sister chromatid separation and progression to anaphase. Using a short hairpin RNA screen targeting components of the ubiquitin-proteasome pathway in human cells, we identified the deubiquitinating enzyme USP44 (ubiquitin-specific protease 44) as a critical regulator of the spindle checkpoint. USP44 is not required for the initial recognition of unattached kinetochores and the subsequent recruitment of checkpoint components. Instead, it prevents the premature activation of the APC by stabilizing the APC-inhibitory Mad2-Cdc20 complex. USP44 deubiquitinates the APC coactivator Cdc20 both in vitro and in vivo, and thereby directly counteracts the APC-driven disassembly of Mad2-Cdc20 complexes (discussed in an accompanying paper). Our findings suggest that a dynamic balance of ubiquitination by the APC and deubiquitination by USP44 contributes to the generation of the switch-like transition controlling anaphase entry, analogous to the way that phosphorylation and dephosphorylation of Cdk1 by Wee1 and Cdc25 controls entry into mitosis.
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PMID:Anaphase initiation is regulated by antagonistic ubiquitination and deubiquitination activities. 1744 75

The Herpes simplex virus type-1 (HSV-1) regulatory protein ICP0, a RING-finger E3 ubiquitin ligase, stimulates the onset of viral lytic replication and the reactivation of quiescent viral genomes from latency. Like many ubiquitin ligases ICP0 induces its own ubiquitination, a process that can lead to its proteasome-dependent degradation. ICP0 counteracts this activity by recruiting the cellular ubiquitin-specific protease USP7/HAUSP. Here we show that ICP0 can also interact with a previously unidentified isoform of USP7 (termed here USP7(beta)). This isoform is not a predominantly ubiquitinated, SUMO-modified, or phosphorylated species of USP7 but is constitutively expressed in a number of different cell types. Like USP7, USP7(beta) binds specifically to an electrophilic ubiquitin probe, indicating that it contains an accessible catalytic core with potential ubiquitin-protease activity. The interaction formed between ICP0 and USP7(beta) requires ICP0 to have an intact USP7-binding domain and results in its susceptibility to ICP0-mediated degradation during HSV-1 infection.
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PMID:Identification of a novel higher molecular weight isoform of USP7/HAUSP that interacts with the Herpes simplex virus type-1 immediate early protein ICP0. 1859 Jul 80

Adjustment of Na+ balance in extracellular fluids is achieved by regulated Na+ transport involving the amiloride-sensitive epithelial Na+ channel (ENaC) in the distal nephron. In this context, ENaC is controlled by a number of hormones, including vasopressin, which promotes rapid translocation of water and Na+ channels to the plasma membrane and long-term effects on transcription of vasopressin-induced and -reduced transcripts. We have identified a mRNA encoding the deubiquitylating enzyme ubiquitin-specific protease 10 (Usp10), whose expression is increased by vasopressin at both the mRNA and the protein level. Coexpression of Usp10 in ENaC-transfected HEK-293 cells causes a more than fivefold increase in amiloride-sensitive Na+ currents, as measured by whole cell patch clamping. This is accompanied by a three- to fourfold increase in surface expression of alpha- and gamma-ENaC, as shown by cell surface biotinylation experiments. Although ENaC is well known to be regulated by its direct ubiquitylation, Usp10 does not affect the ubiquitylation level of ENaC, suggesting an indirect effect. A two-hybrid screen identified sorting nexin 3 (SNX3) as a novel substrate of Usp10. We show that it is a ubiquitylated protein that is degraded by the proteasome; interaction with Usp10 leads to its deubiquitylation and stabilization. When coexpressed with ENaC, SNX3 increases the channel's cell surface expression, similarly to Usp10. In mCCD(cl1) cells, vasopressin increases SNX3 protein but not mRNA, supporting the idea that the vasopressin-induced Usp10 deubiquitylates and stabilizes endogenous SNX3 and consequently promotes cell surface expression of ENaC.
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PMID:Vasopressin-inducible ubiquitin-specific protease 10 increases ENaC cell surface expression by deubiquitylating and stabilizing sorting nexin 3. 1866 80

Homozygous ataxia (ax(J)) mice have reduced expression of ubiquitin-specific protease 14 (Usp14), resulting in severe neuromuscular defects and death by 2 months of age. Transgenic expression of Usp14 exclusively in the nervous system of ax(J) mice (ax(J)-Tg) prevents early lethality and restores motor system function to the ax(J) mice, enabling an analysis of the reproductive capabilities of Usp14-deficient mice. Although female ax(J)-Tg mice had a 75% reduction of Usp14 in the ovaries, they were able to produce normal litters. Ovary transfer experiments also demonstrated that the ovaries of ax(J) mice were capable of producing viable pups. In contrast, male ax(J) and ax(J)-Tg mice displayed a 50% reduction in testicular Usp14 levels and were infertile, indicating that Usp14 is required for development and function of the male reproductive system. Immunohistochemistry experiments showed that Usp14 is found in the redundant nuclear envelope and cytoplasmic droplet of epididymal spermatozoa. Analysis of ax(J) testes demonstrated a 50% reduction in testis weight, a 100-fold reduction in sperm number and the presence of abnormal spermatozoa in the epididymis. Histological examination of the Usp14-deficient testes revealed abnormal spermatogenesis and the presence of degenerating germ cells, indicating that Usp14 and the ubiquitin proteasome system are required for spermatid differentiation during spermiogenesis.
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PMID:Transgenic rescue of ataxia mice reveals a male-specific sterility defect. 1892 13

An affinity purification strategy was developed to characterize human proteasome complexes diversity as well as endogenous proteasome-interacting proteins (PIPs). This single step procedure, initially used for 20 S proteasome purification, was adapted to purify all existing physiological proteasome complexes associated to their various regulatory complexes and to their interacting partners. The method was applied to the purification of proteasome complexes and their PIPs from human erythrocytes but can be used to purify proteasomes from any human sample as starting material. The benefit of in vivo formaldehyde cross-linking as a stabilizer of protein-protein interactions was studied by comparing the status of purified proteasomes and the identified proteins in both protocols (with or without formaldehyde cross-linking). Subsequent proteomics analyses identified all proteasomal subunits, known regulators, and recently assigned partners. Moreover other proteins implicated at different levels of the ubiquitin-proteasome system were also identified for the first time as PIPs. One of them, the ubiquitin-specific protease USP7, also known as HAUSP, is an important player in the p53-HDM2 pathway. The specificity of the interaction was further confirmed using a complementary approach that consisted of the reverse immunoprecipitation with HAUSP as a bait. Altogether we provide a valuable tool that should contribute, through the identification of partners likely to affect proteasomal function, to a better understanding of this complex proteolytic machinery in any living human cell and/or organ/tissue and in different cell physiological states.
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PMID:Affinity purification strategy to capture human endogenous proteasome complexes diversity and to identify proteasome-interacting proteins. 1919 9

Histone acetyltransferases (HATs) play important roles in gene regulation and DNA repair by influencing the accessibility of chromatin to transcription factors and repair proteins. Here, we show that deletion of Gcn5 leads to telomere dysfunction in mouse and human cells. Biochemical studies reveal that depletion of Gcn5 or ubiquitin-specific protease 22 (Usp22), which is another bona fide component of the Gcn5-containing SAGA complex, increases ubiquitination and turnover of TRF1, a primary component of the telomeric shelterin complex. Inhibition of the proteasome or overexpression of USP22 opposes this effect. The USP22 deubiquitinating module requires association with SAGA complexes for activity, and we find that depletion of Gcn5 compromises this association in mammalian cells. Thus, our results indicate that Gcn5 regulates TRF1 levels through effects on Usp22 activity and SAGA integrity.
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PMID:Gcn5 and SAGA regulate shelterin protein turnover and telomere maintenance. 1968 89

The purpose of this study was to screen for genes involved in ovarian carcinogenesis in an attempt to develop an effective molecular-targeted therapy for ovarian cancer. We constructed retroviral expression libraries for the human ovarian cancer cell lines SHIN-3 and TYK-CPr, and performed a focus formation assay with 3T3 cells. As a result, proteasome subunit beta-type 2 (PSMB2), ubiquitin-specific protease 14 (USP14), and keratin 8 (KRT8) were identified from SHIN-3, and polymerase II RNA subunit (POLR2E), chaperonin containing T-complex polypeptide 1 subunit 4 (CCT4), glia maturation factor beta (GMFB), and neuroblastoma ras viral oncogene homolog (NRAS) from TYK-CPr. NRAS gene analysis revealed a CAA --> AAA substitution at codon 61, resulting in a Glu --> Lys change at position 61. When the mutant NRAS was introduced into fibroblasts for its expression, many transformed foci were generated, confirming the transforming ability of the mutant NRAS.
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PMID:Screening for genetic abnormalities involved in ovarian carcinogenesis using retroviral expression libraries. 1978 49

Ubiquitin proteases remove ubiquitin monomers or polymers to modify the stability or activity of proteins and thereby serve as key regulators of signal transduction. Here, we describe the function of the Drosophila ubiquitin-specific protease 36 (dUSP36) in negative regulation of the immune deficiency (IMD) pathway controlled by the IMD protein. Overexpression of catalytically active dUSP36 ubiquitin protease suppresses fly immunity against Gram-negative pathogens. Conversely, silencing dUsp36 provokes IMD-dependent constitutive activation of IMD-downstream Jun kinase and NF-kappaB signaling pathways but not of the Toll pathway. This deregulation is lost in axenic flies, indicating that dUSP36 prevents constitutive immune signal activation by commensal bacteria. dUSP36 interacts with IMD and prevents K63-polyubiquitinated IMD accumulation while promoting IMD degradation in vivo. Blocking the proteasome in dUsp36-expressing S2 cells increases K48-polyubiquitinated IMD and prevents its degradation. Our findings identify dUSP36 as a repressor whose IMD deubiquitination activity prevents nonspecific activation of innate immune signaling.
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PMID:The Drosophila ubiquitin-specific protease dUSP36/Scny targets IMD to prevent constitutive immune signaling. 1983 67

Epstein-Barr nuclear antigen 1 (EBNA-1) is consistently expressed in all EBV-associated gastric carcinomas. We explored its biological effects in gastric carcinoma cells by expressing the protein in two Epstein-Barr virus (EBV)-negative gastric carcinoma cell lines (SCM1 and TMC1). EBNA1-expressing SCM1 and TMC1 cells displayed no significant differences in growth rates, respectively, compared to those of vector-transfected SCM1 and TMC1 cells in vitro. However, EBNA1 was able to enhance tumorigenicity, the growth rate and the malignant histopathological grade in a xenograft nude mice test. We also evaluated whether EBNA1 caused EBNA1-expressing cells to have enhanced tumorigenicity in an immunocompetent host. We showed that EBNA1-expressing LL/2 cells (derived from lung carcinoma of a Swiss mouse) had enhanced tumorigenicity and growth ability in the immunocompetent allograft Balb/c mice test. These results support the expression of EBNA1 in EBV-associated gastric carcinoma being able to provide advantages of EBV-mediated cell growth and transformation, and to enhance the malignant potential in vivo. In a clonogenic assay, we showed that EBNA1 could reduce the sensitivity of gastric carcinoma cells (SCM1 cells) harboring wild-type p53 to cisplatin, but this was not found in mutant p53-bearing TMC1 cells. In addition, we demonstrated that EBNA1-expressing SCM1 cells, but not EBNA1-expressing TMC1 cells, were associated with reduced expression levels of p53. These findings are compatible with EBNA1 efficiently competing with p53 for binding to ubiquitin-specific protease 7, which causes p53 to degrade by the ubiquitin/proteasome system. These findings suggest that EBNA1 expression is able to reduce the p53 protein level, resulting in the inhibition of its functional activities. Finally, our results suggest that EBV infection with EBNA1 expression in gastric carcinomas provides advantages for host cell survival, growth ability and transformation potential involving escape from immunosurveillance and a reduction in the sensitivity to DNA damage or other apoptotic stress stimuli mediated by suppression of the wild-type p53 protein level; these are distinct from the pathogenesis of EBV-negative gastric carcinomas.
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PMID:Expression of Epstein-Barr nuclear antigen 1 in gastric carcinoma cells is associated with enhanced tumorigenicity and reduced cisplatin sensitivity. 1995 44


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