Regulation of Bovine Papillomavirus Replicative Helicase E1 by the Ubiquitin-Proteasome Pathway

ABSTRACT Papillomaviruses maintain their genomes in a relatively constant copy number as stable extrachromosomal plasmids in the nuclei of dividing host cells. The viral initiator of replication, E1, is not detected in papillomavirus-infected cells. Here, we present evidence that E1 encoded by bovine papillomavirus type 1 is an unstable protein that is degraded through the ubiquitin-proteasome pathway. In a cell-free system derived from Xenopus egg extracts, E1 degradation is regulated by both cyclin E/Cdk2 binding and E1 replication activity. Free E1 is readily ubiquitinated and degraded by the proteasome, while it becomes resistant to this degradation pathway when bound to cyclin E/Cdk2 complexes before the start of DNA synthesis. This stabilization is reversed in a process involving E1-dependent replication activity. In transiently transfected cells, E1 is also polyubiquitinated and accumulates when proteasome activity is inhibited. Thus, the establishment and maintenance of a stable number of papillomavirus genomes in latently infected cells are in part a function of regulated ubiquitin-mediated degradation of E1.

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Destabilization of YopE by the Ubiquitin-Proteasome Pathway Fine-Tunes Yop Delivery into Host Cells and Facilitates Systemic Spread ofYersinia enterocoliticain Host Lymphoid Tissue

Infection and Immunity ◽

10.1128/iai.00694-10 ◽

2010 ◽

Vol 79 (3) ◽

pp. 1166-1175 ◽

Cited By ~ 15

Author(s):

Kristin Gaus ◽

Moritz Hentschke ◽

Nicole Czymmeck ◽

Lena Novikova ◽

Konrad Trülzsch ◽

...

Keyword(s):

Lymphoid Tissue ◽

Defense Responses ◽

Host Cells ◽

Virulence Plasmid ◽

Ubiquitin Proteasome Pathway ◽

Systemic Spread ◽

Ubiquitin Proteasome ◽

Infected Cells ◽

Proteasome Pathway

ABSTRACTPathogenicYersiniaspecies inject a panel of Yop virulence proteins by type III protein secretion into host cells to modulate cellular defense responses. This enables the survival and dissemination of the bacteria in the host lymphoid tissue. We have previously shown that YopE of theY. enterocoliticaserogroup O8 is degraded in the host cell through the ubiquitin-proteasome pathway. YopE normally manipulates rearrangements of the actin cytoskeleton and triggers phagocytosis resistance. To shed light into the physiological role of YopE inactivation, we mutagenized the lysine polyubiquitin acceptor sites of YopE in theY. enterocoliticaserogroup O8 virulence plasmid. The resulting mutant strain escaped polyubiquitination and degradation of YopE and displayed increased intracellular YopE levels, which was accompanied by a pronounced cytotoxic effect on infected cells. Despite its intensified activity on cultured cells, theYersiniamutant with stabilized YopE showed reduced dissemination into liver and spleen following enteral infection of mice. Furthermore, the accumulation of degradation-resistant YopE was accompanied by the diminished delivery of YopP and YopH into cultured,Yersinia-infected cells. A role of YopE in the regulation of Yop translocation has already been described. Our results imply that the inactivation of YopE by the proteasome could be a tool to ensure intermediate intracellular YopE levels, which may effectuate optimized Yop injection into host cells. In this regard,Y. enterocoliticaO8 appears to exploit the host ubiquitin proteasome system to destabilize YopE and to fine-tune the activities of the Yop virulence arsenal on the infected host organism.

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The Impact of Paeoniflorin onα-Synuclein Degradation Pathway

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2015/182495 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8

Author(s):

Zenglin Cai ◽

Xinzhi Zhang ◽

Yongjin Zhang ◽

Xiuming Li ◽

Jing Xu ◽

...

Keyword(s):

Chinese Medicine ◽

Traditional Chinese Medicine ◽

Fluorescence Intensity ◽

Cell Damage ◽

Degradation Pathway ◽

Ubiquitin Proteasome Pathway ◽

Pathway Expression ◽

Ubiquitin Proteasome ◽

Proteasome Pathway ◽

The Impact

Paeoniflorin (PF) is the major active ingredient in the traditional Chinese medicine Radix. It plays a neuroprotective role by regulating autophagy and the ubiquitin-proteasome degradation pathway. In this study, we found PF significantly reduced cell damage caused by MPP+, returning cells to normal state. Cell viability significantly improved after 24 h exposure to RAPA and PF in the MPP+ group (allP<0.01). CAT and SOD activities were significantly decreased after PF and RAPA treatment, compared with MPP+ (P<0.001). In addition, MPP+ activated both LC3-II and E1; RAPA increased LC3-II but inhibited E1. PF significantly upregulated both LC3-II (autophagy) and E1 (ubiquitin-proteasome pathway) expression (P<0.001), promoted degradation ofα-synuclein, and reduced cell damage. We show MPP+ enhanced immunofluorescence signal of intracellularα-synuclein and LC3. Fluorescence intensity ofα-synuclein decreased after PF treatment. In conclusion, these data show PF reversed the decline of proteasome activity caused by MPP+ and significantly upregulated both autophagy and ubiquitin-proteasome pathways, promoted the degradation ofα-synuclein, and reduced cell damage. These findings suggest PF is a potential therapeutic medicine for neurodegenerative diseases.

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The ubiquitin–proteasome pathway in viral infectionsThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigator's Forum.

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y05-144 ◽

2006 ◽

Vol 84 (1) ◽

pp. 5-14 ◽

Cited By ~ 90

Author(s):

Guang Gao ◽

Honglin Luo

Keyword(s):

Critical Role ◽

Proteasome Inhibition ◽

Degradation Pathway ◽

Enteroviral Infection ◽

Ubiquitin Proteasome Pathway ◽

Potential Therapeutic Application ◽

Intracellular Protein Degradation ◽

Ubiquitin Proteasome ◽

Proteasome Pathway ◽

And Function

The cellular biological function of the ubiquitin–proteasome pathway as a major intracellular protein degradation pathway, and as an important modulator for the regulation of many fundamental cellular processes has been greatly appreciated over the last decade. The critical role of the ubiquitin–proteasome pathway in viral pathogenesis has become increasingly apparent. Many viruses have been reported to evolve different strategies to utilize the ubiquitin–proteasome pathway for their own benefits. Here, we review the general background and function of the ubiquitin–proteasome pathway, summarize our current understanding of how viruses use this pathway to target cellular proteins, and finally, discuss the roles of this pathway in enteroviral infection, and the potential therapeutic application of proteasome inhibition in myocarditis.

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Turnover of cyclin E by the ubiquitin-proteasome pathway is regulated by cdk2 binding and cyclin phosphorylation.

Genes & Development ◽

10.1101/gad.10.16.1979 ◽

1996 ◽

Vol 10 (16) ◽

pp. 1979-1990 ◽

Cited By ~ 307

Author(s):

B E Clurman ◽

R J Sheaff ◽

K Thress ◽

M Groudine ◽

J M Roberts

Keyword(s):

Cyclin E ◽

Ubiquitin Proteasome Pathway ◽

Ubiquitin Proteasome ◽

Proteasome Pathway

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Role of ubiquitin-proteasome degradation pathway in biogenesis efficiency of β-cell ATP-sensitive potassium channels

AJP Cell Physiology ◽

10.1152/ajpcell.00240.2005 ◽

2005 ◽

Vol 289 (5) ◽

pp. C1351-C1359 ◽

Cited By ~ 43

Author(s):

Fei-Fei Yan ◽

Chia-Wei Lin ◽

Etienne A. Cartier ◽

Show-Ling Shyng

Keyword(s):

Surface Expression ◽

Degradation Pathway ◽

Sulfonylurea Receptor ◽

Membrane Excitability ◽

Β Cells ◽

Β Cell ◽

Ubiquitin Proteasome Pathway ◽

Ubiquitin Proteasome ◽

Proteasome Pathway

ATP-sensitive potassium (KATP) channels of pancreatic β-cells mediate glucose-induced insulin secretion by linking glucose metabolism to membrane excitability. The number of plasma membrane KATP channels determines the sensitivity of β-cells to glucose stimulation. The KATP channel is formed in the endoplasmic reticulum (ER) on coassembly of four inwardly rectifying potassium channel Kir6.2 subunits and four sulfonylurea receptor 1 (SUR1) subunits. Little is known about the cellular events that govern the channel's biogenesis efficiency and expression. Recent studies have implicated the ubiquitin-proteasome pathway in modulating surface expression of several ion channels. In this work, we investigated whether the ubiquitin-proteasome pathway plays a role in the biogenesis efficiency and surface expression of KATP channels. We provide evidence that, when expressed in COS cells, both Kir6.2 and SUR1 undergo ER-associated degradation via the ubiquitin-proteasome system. Moreover, treatment of cells with proteasome inhibitors MG132 or lactacystin leads to increased surface expression of KATP channels by increasing the efficiency of channel biogenesis. Importantly, inhibition of proteasome function in a pancreatic β-cell line, INS-1, that express endogenous KATP channels also results in increased channel number at the cell surface, as assessed by surface biotinylation and whole cell patch-clamp recordings. Our results support a role of the ubiquitin-proteasome pathway in the biogenesis efficiency and surface expression of β-cell KATP channels.

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Nonstructural Protein 5A Impairs DNA Damage Repair: Implications for Hepatitis C Virus-Mediated Hepatocarcinogenesis

Journal of Virology ◽

10.1128/jvi.00178-18 ◽

2018 ◽

Vol 92 (11) ◽

Cited By ~ 9

Author(s):

Tram T. T. Nguyen ◽

Eun-Mee Park ◽

Yun-Sook Lim ◽

Soon B. Hwang

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Molecular Mechanisms ◽

Viral Propagation ◽

Ubiquitin Proteasome Pathway ◽

Damage Repair ◽

Ubiquitin Proteasome ◽

Infected Cells ◽

Proteasome Pathway ◽

Insight Into

ABSTRACT RAD51-associated protein 1 (RAD51AP1) is a member of the multiprotein complexes postulated to carry out RAD51-mediated homologous recombination and DNA repair in mammalian cells. In the present study, we showed that hepatitis C virus (HCV) NS5A directly bound RAD51AP1 and increased the protein level of RAD51AP1 through modulation of the ubiquitin-proteasome pathway. We also demonstrated that RAD51AP1 protein levels were increased in the liver tissues of HCV-infected patients and NS5A-transgenic mice. Importantly, NS5A impaired DNA repair by disrupting the RAD51/RAD51AP1/UAF1 complex and rendered HCV-infected cells more sensitive to DNA damage. Silencing of RAD51AP1 expression resulted in a decrease of viral propagation. We further demonstrated that RAD51AP1 was involved in the assembly step of the HCV life cycle by protecting viral RNA. These data suggest that HCV exploits RAD51AP1 to promote viral propagation and thus that host DNA repair is compromised in HCV-infected cells. Overall, our findings provide mechanistic insight into the pathogenesis of HCV infection. IMPORTANCE Chronic infection with HCV is the leading cause of hepatocellular carcinoma (HCC). However, the molecular mechanisms underlying HCV-induced HCC are not fully understood. Here we demonstrate that the HCV NS5A protein physically interacts with RAD51AP1 and increases the RAD51AP1 protein level through modulation of the ubiquitin-proteasome pathway. HCV coopts host RAD51AP1 to protect viral RNA at an assembly step of the HCV life cycle. Note that the RAD51 protein accumulates in the cytoplasm of HCV-infected cells, and thus the RAD51/RAD51AP1/UAF1-mediated DNA damage repair system in the nucleus is compromised in HCV-infected cells. Our data may provide new insight into the molecular mechanisms of HCV-induced pathogenesis.

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