scholarly journals Regulation of O-Linked N-Acetyl Glucosamine Transferase (OGT) through E6 Stimulation of the Ubiquitin Ligase Activity of E6AP

2021 ◽  
Vol 22 (19) ◽  
pp. 10286
Author(s):  
Kangli Peng ◽  
Ruochuan Liu ◽  
Caiwei Jia ◽  
Yiyang Wang ◽  
Geon H. Jeong ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Ubiquitin Ligase ◽  
Hek293 Cells ◽  
Cellular Proteins ◽  
Cellular Processes ◽  
Endogenous Expression ◽  
Protein Ubiquitination ◽  
Ubiquitin Ligase Activity ◽  
E6 Protein ◽  
Stimulation Of

Glycosyltransferase OGT catalyzes the conjugation of O-linked β-D-N-acetylglucosamine (O-GlcNAc) to Ser and Thr residues of the cellular proteins and regulates many key processes in the cell. Here, we report the identification of OGT as a ubiquitination target of HECT-type E3 ubiquitin (UB) ligase E6AP, whose overexpression in HEK293 cells would induce the degradation of OGT. We also found that the expression of E6AP in HeLa cells with the endogenous expression of the E6 protein of the human papillomavirus (HPV) would accelerate OGT degradation by the proteasome and suppress O-GlcNAc modification of OGT substrates in the cell. Overall, our study establishes a new mechanism of OGT regulation by the ubiquitin­–proteasome system (UPS) that mediates the crosstalk between protein ubiquitination and O-GlcNAcylation pathways underlying diverse cellular processes.

scholarly journals Human Papillomavirus 16 (HPV-16), HPV-18, and HPV-31 E6 Override the Normal Phosphoregulation of E6AP Enzymatic Activity

2017 ◽  
Vol 91 (22) ◽  
Author(s):  
Jayashree Thatte ◽  
Lawrence Banks
Keyword(s):  
Human Papillomavirus ◽  
Enzymatic Activity ◽  
Ubiquitin Ligase ◽  
Subcellular Distribution ◽  
Hpv 16 ◽  
Human Papillomavirus 16 ◽  
Hpv E6 ◽  
Ubiquitin Ligase Activity ◽  
Hpv 18 ◽  
Stimulation Of

ABSTRACT The human papillomavirus (HPV) E6 oncoproteins recruit the cellular ubiquitin ligase E6AP/UBE3A to target cellular substrates for proteasome-mediated degradation, and one consequence of this activity is the E6 stimulation of E6AP autoubiquitination and degradation. Recent studies identified an autism-linked mutation within E6AP at T485, which was identified as a protein kinase A phosphoacceptor site and which could directly regulate E6AP ubiquitin ligase activity. In this study, we have analyzed how T485-mediated regulation of E6AP might affect E6 targeting of some of its known substrates. We show that modulation of T485 has no effect on the ability of E6 to direct either p53 or Dlg for degradation. Furthermore, T485 regulation has no effect on HPV-16 or HPV-31 E6-induced autodegradation of E6AP but does affect HPV-18 E6-induced autodegradation of E6AP. In cells derived from cervical cancers, we find low levels of both phosphorylated and nonphosphorylated E6AP in the nucleus. However, ablation of E6 results in a dramatic accumulation of phospho-E6AP in the cytoplasm, whereas nonphosphorylated E6AP accumulates primarily in the nucleus. Interestingly, E6AP phosphorylation at T485 confers association with 14-3-3 proteins, and this interaction seems to be important, in part, for the ability of E6 to recruit phospho-E6AP into the nucleus. These results demonstrate that HPV E6 overrides the normal phosphoregulation of E6AP, both in terms of its enzymatic activity and its subcellular distribution. IMPORTANCE Recent reports demonstrate the importance of phosphoregulation of E6AP for its normal enzymatic activity. Here, we show that HPV E6 is capable of overriding this regulation and can promote degradation of p53 and Dlg regardless of the phosphorylation status of E6AP. Furthermore, E6 interaction with E6AP also significantly alters how E6AP is subject to autodegradation and suggests that this is not a simple stimulation of an already-existing activity but rather a redirection of E6AP activity toward itself. Furthermore, E6-mediated regulation of the subcellular distribution of phospho-E6AP appears to be dependent, in part, upon the 14-3-3 family of proteins.

scholarly journals The role of SCF ubiquitin-ligase complex at the beginning of life

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Jiayan Xie ◽  
Yimei Jin ◽  
Guang Wang
Keyword(s):  
Cell Cycle ◽  
Ubiquitin Ligase ◽  
Cellular Proteins ◽  
Cell Cycle Regulators ◽  
Signal Transducers ◽  
E3 Ligases ◽  
Cellular Processes ◽  
Ubiquitin Ligase Complex ◽  
Scf Ubiquitin Ligase

AbstractAs the largest family of E3 ligases, the Skp1-cullin 1-F-box (SCF) E3 ligase complex is comprised of Cullins, Skp1 and F-box proteins. And the SCF E3 ubiquitin ligases play an important role in regulating critical cellular processes, which promote degradation of many cellular proteins, including signal transducers, cell cycle regulators, and transcription factors. We review the biological roles of the SCF ubiquitin-ligase complex in gametogenesis, oocyte-to-embryo transition, embryo development and the regulation for estrogen and progestin. We find that researches about the SCF ubiquitin-ligase complex at the beginning of life are not comprehensive, thus more in-depth researches will promote its eventual clinical application.

scholarly journals The Global Transcriptional Effects of the Human Papillomavirus E6 Protein in Cervical Carcinoma Cell Lines Are Mediated by the E6AP Ubiquitin Ligase

2005 ◽  
Vol 79 (6) ◽  
pp. 3737-3747 ◽  
Author(s):  
Melissa L. Kelley ◽  
Kerri E. Keiger ◽  
Chan Jae Lee ◽  
Jon M. Huibregtse
Keyword(s):  
Human Papillomavirus ◽  
Cell Lines ◽  
Ubiquitin Ligase ◽  
Telomerase Activity ◽  
Transcriptional Program ◽  
Hpv E6 ◽  
Amplification Protocol ◽  
Independent Functions ◽  
Interfering Rna ◽  
E6 Protein

ABSTRACT The function of the human papillomavirus (HPV) E6 protein that is most clearly linked to carcinogenesis is the targeted degradation of p53, which is dependent on the E6AP ubiquitin ligase. Additional functions have been attributed to E6, including the stimulation of telomerase activity and the targeted degradation of other cellular proteins, but in most cases it is unclear whether these activities are also E6AP dependent. While E6 clearly influences the transcriptional program of HPV-positive cell lines through the inactivation of p53, it has been shown that at least a subset of its p53-independent functions are also reflected in the transcriptional program. For this study, we have determined the extent to which E6AP is involved in mediating the set of E6 functions that impact on the global transcriptional program of HPV-positive cell lines. The transcriptional profiles of ∼31,000 genes were characterized for three cell lines (HeLa, Caski, and SiHa cells) after small interfering RNA (siRNA)-mediated silencing of E6 or E6AP. We found that E6 and E6AP siRNAs elicited nearly identical alterations in the transcriptional profile of each cell line. Some of the expression alterations were apparent secondary effects of p53 stabilization, while the basis of most other changes was not reconcilable with previously proposed E6 functions. While expression changes of the TERT gene (telomerase catalytic subunit) were not revealed by the array, telomerase repeat amplification protocol assays showed that both E6 and E6AP knockouts resulted in a suppression of telomerase activity. Together, these results suggest that E6AP mediates a broad spectrum of E6 functions, including virtually all functions that impact on the transcriptional program of HPV-positive cell lines.

scholarly journals Cell signalling pathway regulation by RanBPM: molecular insights and disease implications

Open Biology ◽  
2017 ◽  
Vol 7 (6) ◽  
pp. 170081 ◽  
Author(s):  
Louisa M. Salemi ◽  
Matthew E. R. Maitland ◽  
Christina J. McTavish ◽  
Caroline Schild-Poulter
Keyword(s):  
Ubiquitin Ligase ◽  
Critical Role ◽  
Cell Signalling ◽  
E3 Ubiquitin Ligase ◽  
Cellular Processes ◽  
Ubiquitin Ligase Activity ◽  
Complex Functions ◽  
Pathological Development ◽  
Pathway Regulation ◽  
High Level

RanBPM (Ran-binding protein M, also called RanBP9) is an evolutionarily conserved, ubiquitous protein which localizes to both nucleus and cytoplasm. RanBPM has been implicated in the regulation of a number of signalling pathways to regulate several cellular processes such as apoptosis, cell adhesion, migration as well as transcription, and plays a critical role during development. In addition, RanBPM has been shown to regulate pathways implicated in cancer and Alzheimer's disease, implying that RanBPM has important functions in both normal and pathological development. While its functions in these processes are still poorly understood, RanBPM has been identified as a component of a large complex, termed the CTLH (C-terminal to LisH) complex. The yeast homologue of this complex functions as an E3 ubiquitin ligase that targets enzymes of the gluconeogenesis pathway. While the CTLH complex E3 ubiquitin ligase activity and substrates still remain to be characterized, the high level of conservation between the complexes in yeast and mammals infers that the CTLH complex could also serve to promote the degradation of specific substrates through ubiquitination, therefore suggesting the possibility that RanBPM's various functions may be mediated through the activity of the CTLH complex.

scholarly journals To Ubiquitinate or Not to Ubiquitinate: TRIM17 in Cell Life and Death

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1235
Author(s):  
Meenakshi Basu-Shrivastava ◽  
Alina Kozoriz ◽  
Solange Desagher ◽  
Iréna Lassot
Keyword(s):  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Brain Regions ◽  
Cell Physiology ◽  
Life And Death ◽  
Cellular Processes ◽  
Cell Life ◽  
Ubiquitin Ligase Activity ◽  
Human Disorders ◽  
Trim Proteins

TRIM17 is a member of the TRIM family, a large class of RING-containing E3 ubiquitin-ligases. It is expressed at low levels in adult tissues, except in testis and in some brain regions. However, it can be highly induced in stress conditions which makes it a putative stress sensor required for the triggering of key cellular responses. As most TRIM members, TRIM17 can act as an E3 ubiquitin-ligase and promote the degradation by the proteasome of substrates such as the antiapoptotic protein MCL1. Intriguingly, TRIM17 can also prevent the ubiquitination of other proteins and stabilize them, by binding to other TRIM proteins and inhibiting their E3 ubiquitin-ligase activity. This duality of action confers several pivotal roles to TRIM17 in crucial cellular processes such as apoptosis, autophagy or cell division, but also in pathological conditions as diverse as Parkinson’s disease or cancer. Here, in addition to recent data that endorse this duality, we review what is currently known from public databases and the literature about TRIM17 gene regulation and expression, TRIM17 protein structure and interactions, as well as its involvement in cell physiology and human disorders.

scholarly journals Virus-host protein-protein interactions between human papillomavirus 16 E6 A1 and D2/D3 sub-lineages: variances and similarities

2020 ◽  
Author(s):  
Guillem Dayer ◽  
Mehran L. Masoom ◽  
Melissa Togtema ◽  
Ingeborg Zehbe
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
Asian American ◽  
Protein Interactions ◽  
Host Protein ◽  
Cellular Proteins ◽  
Loss Of Function ◽  
Protein Protein Interactions ◽  
Host Proteins ◽  
E6 Protein

AbstractHigh-risk strains of human papillomavirus are causative agents for cervical and other mucosal cancers with type 16 being the most frequent. Compared to the European Prototype (A1, denoted “EP”), the Asian-American (D2/D3, denoted “AA”) sub-lineage or “variant” is reported to have increased abilities to promote carcinogenesis. Few global interactome studies have looked at protein-protein interactions (PPIs) between host proteins and variants of the key transforming E6 protein. We applied a primary human foreskin keratinocyte model transduced with EP and AA variant E6 genes and co-immunoprecipitated expressed E6 proteins along with interacting cellular proteins to detect virus-host binding partners. We reasoned that, due to single nucleotide polymorphisms, AAE6 and EPE6 may have unique PPIs with host cellular proteins—conferring gain or loss of function—resulting in varied abilities to promote carcinogenesis. Using liquid chromatography-mass spectrometry and stringent interactor selection criteria based on the number of peptides, we identified 25 candidates: 6 unique to each of AAE6 and EPE6, along with 13 E6 targets common to both AAE6 and EPE6. We also applied a more inclusive process based on pathway selection and discovered 171 target proteins: 90 unique AAE6 and 61 unique EPE6 along with 20 common E6 targets between the two sub-lineages. Interpretations for both approaches were made using databases such as UniProt, BioGRID and Reactome. Detected E6 targets are implicated in important hallmarks of cancer: deregulating Notch and other signaling, energetics and hypoxia, DNA replication and repair, and immune response. Validation experiments, such as reverse co-immunoprecipitation and RNA interference, are required to substantiate these findings. Here, we provide an unprecedented resource for new research questions in HR HPV biology. The current data also underline our lab’s driving hypothesis that E6, being a “master regulator” in HPV-positive cancers, is an excellent candidate for anti-cancer treatment strategies.Author SummaryChronic infection with high-risk human papillomavirus (HPV) type 16 is the most prevalent cause of cervical and other mucosal cancers. The E6 oncoproteins of the European Prototype (EP) and the Asian-American (AA) HPV variants differentially promote carcinogenesis. We looked at protein-protein interactions between host proteins and two key HPV variant E6 proteins of these strains to reveal how high risk HPVs cause cancer, based on the proteins they bind to in infected cells. Our methodology combined molecular biology and data mining techniques using widely available databases. We confirmed and discovered novel virus-host associations that explained how HPV AA and EP variants differ in their carcinogenic capabilities, and confirmed the candidacy of the E6 protein as a viable target for HPV therapies.

scholarly journals Phosphorylation and negative regulation of CONSTITUTIVELY PHOTOMORPHOGENIC 1 by PINOID in Arabidopsis

2017 ◽  
Vol 114 (25) ◽  
pp. 6617-6622 ◽  
Author(s):  
Fang Lin ◽  
Dongqing Xu ◽  
Yan Jiang ◽  
Haodong Chen ◽  
Liumin Fan ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Posttranslational Modification ◽  
Regulatory Mechanism ◽  
E3 Ubiquitin Ligase ◽  
Negative Regulation ◽  
Negative Regulator ◽  
Cellular Processes ◽  
Ubiquitin Ligase Activity

CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) plays crucial roles in various cellular processes via its E3 ubiquitin ligase activity in organisms, ranging from fungi to humans. As a key component in regulating various biological events, COP1 itself is precisely controlled at multiple layers. Here, we report a negative regulator of COP1, PINOID (PID), which positively mediates photomorphogenic development. Specifically, PID genetically and physically interacts with COP1 and directly phosphorylates COP1 at Ser20. As a result, this posttranslational modification serves to repress COP1 activity and promote photomorphogenesis. Our findings signify a key regulatory mechanism for precisely maintaining COP1 activity, thereby ensuring appropriate development in plants.

scholarly journals Regulation of mitophagy by the Gp78 E3 ubiquitin ligase

2013 ◽  
Vol 24 (8) ◽  
pp. 1153-1162 ◽  
Author(s):  
Min Fu ◽  
Pascal St-Pierre ◽  
Jay Shankar ◽  
Peter T. C. Wang ◽  
Bharat Joshi ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Fluorescent Protein ◽  
Mitochondrial Protein ◽  
E3 Ubiquitin Ligase ◽  
Mitochondrial Fusion ◽  
Hek293 Cells ◽  
Chain Elongation ◽  
Mitochondrial Depolarization ◽  
Ubiquitin Ligase Activity ◽  
Sirna Knockdown

Glycoprotein 78 (Gp78) is a critical E3 ubiquitin ligase in endoplasmic reticulum–associated degradation. Overexpression of Flag-tagged Gp78 (Flag-gp78), but not Flag-gp78 mutated in its RING-finger domain (Flag-RINGmut) with deficient ubiquitin ligase activity, induces mitochondrial fragmentation and ubiquitination and proteasome-dependent degradation of the mitofusin (Mfn) mitochondrial fusion factors Mfn1/Mfn2. After mitochondrial depolarization with carbonyl cyanide m-chlorophenylhydrazone (CCCP), Flag-gp78 induced a threefold loss of depolarized mitochondria and significant loss of the inner mitochondrial protein OxPhosV. Flag-gp78–dependent loss of OxPhosV, but not Mfn1 or Mfn2, was prevented by small interfering RNA (siRNA) knockdown of the autophagy protein Atg5 in CCCP-treated cells. Gp78-induced mitophagy required ubiquitin ligase activity, as it is not observed upon transfection of Flag-RINGmut or cotransfection of Flag-gp78 with ubiquitin mutated at three critical lysine residues (K29, 48, 63R) involved in polyubiquitin chain elongation. Short hairpin RNA knockdown of Gp78 in HT-1080 fibrosarcoma cells increased mitofusin levels and reduced depolarization-induced mitophagy, whereas siRNA knockdown showed that Mfn1, but not Mfn2, was required for Gp78-dependent depolarization-induced mitophagy. Mitochondrial depolarization induced Gp78-dependent expression of the autophagic marker LC3II and recruitment of enhanced green fluorescent protein–LC3 to the Gp78- and calnexin-labeled, mitochondria-associated ER. Finally, Gp78-induced mitophagy is Parkin independent, as it occurs in Parkin-null HeLa cells and upon siRNA-mediated Parkin knockdown in HEK293 cells. This study therefore describes a novel role for the ER-associated Gp78 ubiquitin ligase and the Mfn1 mitochondrial fusion factor in mitophagy.

E3 ubiquitin ligases

2005 ◽  
Vol 41 ◽  
pp. 15-30 ◽  
Author(s):  
Helen C. Ardley ◽  
Philip A. Robinson
Keyword(s):  
Protein Complexes ◽  
Loss Of Function ◽  
Direct Role ◽  
Cellular Processes ◽  
Substrate Protein ◽  
Protein Ubiquitination ◽  
C Terminus ◽  
Full Complement ◽  
Spatio Temporal ◽  
Eukaryotic Organisms

The selectivity of the ubiquitin–26 S proteasome system (UPS) for a particular substrate protein relies on the interaction between a ubiquitin-conjugating enzyme (E2, of which a cell contains relatively few) and a ubiquitin–protein ligase (E3, of which there are possibly hundreds). Post-translational modifications of the protein substrate, such as phosphorylation or hydroxylation, are often required prior to its selection. In this way, the precise spatio-temporal targeting and degradation of a given substrate can be achieved. The E3s are a large, diverse group of proteins, characterized by one of several defining motifs. These include a HECT (homologous to E6-associated protein C-terminus), RING (really interesting new gene) or U-box (a modified RING motif without the full complement of Zn2+-binding ligands) domain. Whereas HECT E3s have a direct role in catalysis during ubiquitination, RING and U-box E3s facilitate protein ubiquitination. These latter two E3 types act as adaptor-like molecules. They bring an E2 and a substrate into sufficiently close proximity to promote the substrate's ubiquitination. Although many RING-type E3s, such as MDM2 (murine double minute clone 2 oncoprotein) and c-Cbl, can apparently act alone, others are found as components of much larger multi-protein complexes, such as the anaphase-promoting complex. Taken together, these multifaceted properties and interactions enable E3s to provide a powerful, and specific, mechanism for protein clearance within all cells of eukaryotic organisms. The importance of E3s is highlighted by the number of normal cellular processes they regulate, and the number of diseases associated with their loss of function or inappropriate targeting.

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